User:Marshallsumter/Radiation astronomy2/Rocks

Sin-Kamen (Синь-Камень, in Russian literally – Blue Stone, or Blue Rock) is a type of pagan sacred stones, widespread in Russia, in areas historically inhabited by both Eastern Slavic (Russian), and Uralic tribes (Merya, Muroma ).

While in the majority of cases, the stones belonging to the Blue Stones type, have a black, or dark gray color, this particular stone [in the image] does indeed look dark blue, when wet.

"Several types of rock surface materials can be recognized at the two sites [Viking Lander 1 and Viking Lander 2]; dark, relatively 'blue' rock surfaces are probably minimally weathered igneous rock, whereas bright rock surfaces, with a green/(blue + red) ratio higher than that of any other surface material, are interpreted as a weathering product formed in situ on the rock."

At second right is an approximately natural color image of the asteroid 243 Ida. "There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right-hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron-bearing minerals in these areas."

"The [Sloan Digital Sky Survey] SDSS “blue” asteroids are related to the C-type (carbonaceous) asteroids, but not all of them are C-type. They are a mixture of C-, E-, M-, and P-types."

Rocks
Rocks are a bound aggregate of minerals with usually a large geographic extent.

Occasionally, a rock is composed of only one mineral. But a crystal of the mineral fluorite in your hand is a stone rather than a rock.

A rock is a naturally occurring solid aggregate of one or more minerals or mineraloids.

Def. any "natural material with a distinctive composition of minerals" is called a rock.

Beta particles
Excessive "26Mg [has] been reported in meteoritic carbonaceous chondrites [...] which demonstrate an excess of 26Mg of up to 40% combined with essentially solar concentrations of 24Mg and 25Mg. Many of the data are well correlated with the 27Al content of the samples, and this is interpreted as evidence that the excess 26Mg has arisen from the in situ decay (via positron emission and electron capture) of the ground state of 26Al in these minerals."

X-rays
On September 20, the X-Ray Laboratory at the Faculty of Geological Sciences, Mayor de San Andres University, La Paz, Bolivia, published a report of their analysis of a small sample of material recovered from the impact site. They detected iron, nickel, cobalt, and traces of iridium &mdash; elements characteristic of the elemental composition of meteorites. The quantitative proportions of silicon, aluminum, potassium, calcium, magnesium, and phosphorus are incompatible with rocks that are normally found at the surface of the Earth.

In X-ray wavelengths, many scientists are investigating the scattering of X-rays by interstellar dust, and some have suggested that astronomical X-ray sources would possess diffuse haloes, due to the dust.

Ultraviolets
"Spectrally blue (B-type) asteroids are rare, with the second discovered asteroid, Pallas, being the largest and most famous example."

"[T]he negative optical spectral slope of some B-type asteroids is due to the presence of a broad absorption band centered near 1.0 μm. The 1 μm band can be matched in position and shape using magnetite (Fe3O4), which is an important indicator of past aqueous alteration in the parent body. ... Observations of B-type asteroid (335) Roberta in the 3 μm region reveal an absorption feature centered at 2.9 μm, which is consistent with the absorption due to phyllosilicates (another hydration product) observed in CI chondrites. ... at least some B-type asteroids are likely to have incorporated significant amounts of water ice and to have experienced intensive aqueous alteration."

In 1911, Professor Robert W. Wood used ultraviolet photography to take images of the crater area. He discovered the plateau had an anomalous appearance in the ultraviolet, and an area to the north appeared to give indications of a sulfur deposit. This colorful area is sometimes referred to as "Wood's Spot", an alternate name for the Aristarchus Plateau.

Spectra taken of this crater during the Clementine mission were used to perform mineral mapping. The data indicated that the central peak is a type of rock called anorthosite, which is a slow-cooling form of igneous rock composed of plagioclase feldspar. By contrast the outer wall is troctolite, a rock composed of equal parts plagioclase and olivine.

The Aristarchus region was part of a Hubble Space Telescope study in 2005 that was investigating the presence of oxygen-rich glassy soils in the form of the mineral ilmenite. Baseline measurements were made of the Apollo 15 and Apollo 17 landing sites, where the chemistry is known, and these were compared to Aristarchus. The Hubble Advanced Camera for Surveys was used to photograph the crater in visual and ultraviolet light. The crater was determined to have especially rich concentrations of ilmenite, a titanium oxide mineral that could potentially be used in the future by a lunar settlement for extracting oxygen.

Opticals
The analysis of high-resolution, near-infrared and [ultraviolet] UV spectra obtained by the Galileo spacecraft and from the ground has revealed various non-ice materials: magnesium- and iron-bearing hydrated silicates, carbon dioxide, sulfur dioxide, and possibly ammonia and various organic compounds. Spectral data indicate that the moon's surface is extremely heterogeneous at the small scale. Small, bright patches of pure water ice are intermixed with patches of a rock–ice mixture and extended dark areas made of a non-ice material.

Violets
The purple tone of the foreground rocks has been seen in other rocks where Curiosity's Chemical and Mineralogy (CheMin) instrument has detected hematite.

Blues
"Nine out of 10 well-characterized Apollo 17 breccia matrices fall into Group 2, and this includes both the blue-grey breccias which are the dominant rock type at this site".

"A 1953 telescopic photograph of a flash on the Moon is the only unequivocal record of the rare crash of an asteroid-sized body onto the lunar surface. ... A search of images from the Clementine mission reveals an ∼1.5-km high-albedo, blue, fresh-appearing crater with an associated ejecta blanket at the location of the flash."

In terms of reflectance from the lunar surface, "the very dark 'blue' maria [are] such as found in Mare Tranquillitatis."

"[T]he slope of the reflectance spectrum in the blue and ultraviolet ... is directly related to the percent TiO2 in the [lunar] surface soil (Charette et al., 1974)."

Cyans
“[A]ll the blue basalt types (high in UV/VIS ratio [0.40/0.56 µm]) are also the darkest mare soils.” Both Luna 24 and Apollo 12 soil samples are from mare soils that reflect primarily cyan that is likely due to the presence of TiO2 in the soils.

"Previous work has suggested that a cyan color in the multispectral frame represents highland material, and that yellows and greens are freshly excavated basalts. However, we have recently found that a cyan color can also result from a freshly excavated high-Ti basalt."

Greens
"During its mission, the Galileo spacecraft returned a number of images of Earth's only natural satellite. Galileo surveyed the moon on Dec. 7, 1992, on its way to explore the Jupiter system in 1995-1997."

"This color mosaic was assembled from 18 images taken by Galileo's imaging system through a green filter. On the upperleft is the dark, lava-filled Mare Imbrium, Mare Serenitatis (middle left), Mare Tranquillitatis (lower left), and Mare Crisium, the dark circular feature toward the bottom of the mosaic. Also visible in this view are the dark lava plains of the Marginis and Smythii Basins at the lower right. The Humboldtianum Basin, a 400-mile impact structure partly filled with dark volcanic deposits, is seen at the center of the image."

Oranges
"Crystallized spheres of orange glass from Shorty Crater at the Apollo 17 site are ... the characteristic ingredient of the dark mantling deposit of the Taurus-Littrow region."

"The reflectance properties of the orange glass are highly distinctive. There are two broad absorption bands, one near 1.15 µm and the other near 1.9 µm that arise from Fe2+ on octahedral and tetrahedral sites, respectively ... The weak absorption near 0.5 µm probably arises from Ti3+, and the absorption edge extending into the visible region is due largely to oxygen-titanium charge transfer".

Reds
"There is a general increase in 'redness' with heliocentric distance in the outer belt asteroids going from the moderately red P asteroids, through the redder D asteroids, to the much redder Z asteroids."

Infrareds
"One of Jupiter’s moons has unleashed a series of huge volcanic eruptions over a hellish 2 week period that were so bright they could be studied in detail by ground based observatories."

“We typically expect one huge outburst every one or two years, and they’re usually not this bright.”

“Here [in the image on the right] we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”

“These new events are in a relatively rare class of eruptions on Io because of their size and astonishingly high thermal emission. The amount of energy being emitted by these eruptions implies lava fountains gushing out of fissures at a very large volume per second, forming lava flows that quickly spread over the surface of Io.”

"While recording the eruptions that occurred in the moon’s southern hemisphere on Aug. 15, 2013, the researchers saw the brightest emanate from a caldera called Rarog Patera, which produced a 50 square-mile, 30 foot-thick lava flow — enough lava to cover Manhattan Island. Another eruption that was generated by the caldera Heno Patera produced a flow covering 120 square miles. Both eruptions generated “curtains of fire” as lava blasted from long fissures in Io’s crust."

"Images of Io obtained at different infrared wavelengths (in microns, μm, or millionths of a meter) with the W. M. Keck Observatory’s 10-meter Keck II telescope on Aug. 15, 2013 (a-c) and the Gemini North telescope on Aug. 29, 2013 (d). The bar on the right of each image indicates the intensity of the infrared emission. Note that emissions from the large volcanic outbursts on Aug. 15 at Rarog and Heno Paterae have substantially faded by Aug. 29. A second bright spot is visible to the north of the Rarog and Heno eruptions in c and to the west of the outburst in d. This hot spot was identified as Loki Patera, a lava lake that appeared to be particularly active at the same time."

Moon
In the image at right, planetary geologist and NASA astronaut Harrison "Jack" Schmitt collects lunar samples during the Apollo 17 mission.

"Recent scans of magnetized lunar rocks that show no evidence of effects from cosmic impacts now provide strong evidence that the moon had a magnetic field".

"Earth's magnetic field is currently 50 microteslas in strength. The early moon may have had a magnetic field that was bigger, maybe up to more than 70 microteslas."

Allan Hills A81005 or ALH A81005 (sometimes also named without the "A" in front of the number) was the first lunar meteorite found on Earth. It was found in 1982 in the Allan Hills at the end of the Transantarctic Mountains, during a meteorite gathering expedition (ANSMET).

ALH A81005 was found on 17 January 1982 by John Schutt and Ian Whillans. It is named after the Allan Hills, a mountain chain in Antarctica where many meteorites are gathered by expeditions. The large number of meteorites collected in Antarctica and the lack of geographic terms that could be used for names have led to the adaption of the "Antarctic rules" for meteorite naming. Every meteorite found in Antarctica receives the names of the collection area (Allan Hills) and a number. The number consists of the year the expedition started "81" and a three digit number that is given out consecutively (005). The "A" in front of the number stands for meteorites collected by ANSMET expeditions and can be considered optional. The definition of the year is used because the year changes during the Austral summer season (December to March) and this avoids samples from one expedition having different years. This is the reason ALH A81005 has the year "81" in its name despite being found on 17 January 1982.

ALH A81005 measures 3 xx. It has a dark fusion crust on the outside. The interior is made up of a black to dark grey groundmass (matrix) with larger grey and white angular crystals (clasts). This appearance is typical for breccias, including those originating on Earth. The size of the larger crystals ranges from sub-millimeter to 8 mm in diameter.

Thin section analysis revealed that the crystals are mostly plagioclase, with some pyroxene and olivine. It was also discovered that the meteorite had similarities to terrestrial gabbro or basalt. Microprobe analysis showed that the plagioclase was very calcium-rich. The crystals are a solid solution of 97% anorthite and 3% albite. The pyroxenes have a variable composition lying between enstatite, ferrosilite and wollastonite. The olivine is a solid solution of 11 to 40% fayalite with the rest being forsterite]]. ALH A81005 is classified as a "lunar anorthosite breccia" and belongto the group "lunar anorthosite" (abbreviated Lun-A).

M3 found a rock dominated by Mg-spinel with no detectable pyroxene or olivine present (<5%) occurring along the western inner ring of Moscoviense Basin (as one of several discrete areas). The occurrence of this spinel does not easily fit with current lunar-crustal evolution models.

Earth
The first image on the right is an aerial image of the ice cap on Ellesmere Island, Canada.

Oblique images such as the one on the second lower right are taken by astronauts looking out from the ISS at an angle, rather than looking straight downward toward the Earth (a perspective called a nadir view), as is common with most remotely sensed data from satellites. An oblique view gives the scene a more three-dimension quality, and provides a look at the vertical structure of the volcanic plume. While much of the island is covered in green vegetation, grey deposits that include pyroclastic flows and volcanic mud-flows (lahars) are visible extending from the volcano toward the coastline. When compared to its extent in earlier views, the volcanic debris has filled in more of the eastern coastline. Urban areas are visible in the northern and western portions of the island; they are recognizable by linear street patterns and the presence of bright building rooftops. The silver-grey appearance of the Caribbean Sea surface is due to sun-glint, which is the mirror-like reflection of sunlight off the water surface back towards the hand-held camera on-board the ISS. The sun-glint highlights surface wave patterns around the island.

The image on the left is an aerial view of the Barringer Meteor Crater. Fragments of an iron-nickel meteorite have been found in the crater confirming its origin as an impact crater.

Rock forms
Rock forms are geomorphic land forms made of specific rock types.

Arêtes
Def. a "very thin ridge of rock" is called an arête.

"An earlier [...] glacial episode, herein termed the Altonah Glaciation, is indicated by an extensive lateral moraine beyond the mouth of Yellowstone canyon as well as moraines in Lake Fork and Uinta River canyons. At higher elevations, alpine glacial landforms, including cirques, rock glaciers, arêtes, and hanging valleys are ubiquitous."

"Arêtes and cols are most common in the south-central and southwestern Uinta Mountains, where accumulation areas of glaciers were largest and the development of ice caps that drained into multiple valleys was common. In the south-central Uintas, the most prominent arêtes have more than 450 m of relief and are more than 10 km in length. In the southeastern Uintas, rounded unglaciated divides locally termed “bollies” are more common than narrow arêtes. Examples of these features include broad divides that separate glacial valleys in the headwaters of Dry Fork and Ashley Creeks [...]."

Canyons
On the right is an example of a river canyon, specifically the Grand Canyon in Arizona, USA.

Def. a "valley, especially a long, narrow, steep valley, cut in rock by a river" is called a canyon, or a river canyon.

Def. a deep gorge is called a canyon.

Cliffs
The cliff in the image on the right is part of a karst landscape formed by water and plants on calcareous (probably) limestone.

"This photo [on the left] shows clearly why these glacial deposits are called boulder clay, consisting as they are of clay and stones of various sizes up to and including large boulders. Till is another name for boulder clay." The image is of an eroded boulder-clay cliff near to Trefor, Gwynedd, Great Britain.

Def. a "vertical (or nearly vertical) rock face" is called a cliff.

Glaciers
Def. "a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer" is called a glacier.

Mountains
Def. a "large mass of earth and rock, rising above the common level of the earth or adjacent land, usually given by geographers as above 1000 feet in height (or 304.8 metres), though such masses may still be described as hills in comparison with larger mountains" is called a mountain.

Pavements
Def. a more or less horizontal, hard expanse of bare rock as a surface is called a pavement.

On the right are two images of a limestone pavement which is part of a karst topography.

On the left is a desert pavement in southeastern California.

A pavement such as the one on the second left covered with pieces that are similarly shaped is referred to as a tessellated pavement.

Volcanic bombs
Def. "distinctively shaped [natural] projectiles ... which acquired their shape essentially before landing" are called bombs.

Def. a bomb "ejected from a volcanic vent" is called a volcanic bomb.

Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.

The image at top right is an "[a]ccretionary lava ball [coming] to rest on the grass after rolling off the top of an ‘a‘a flow in Royal Gardens subdivision. Accretionary lava balls form as viscous lava is molded around a core of already solidified lava."

Volcanic bombs cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains making them extrusive igneous rocks. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.

Volcanic bombs can be extremely large; the 1935 eruption of Mount Asama in Japan expelled bombs measuring 5–6 m in diameter up to 600 m from the vent. A large volcanic bomb is shown in the third image at right from Strohn, Germany.

Volcanic bombs are known to occasionally explode from internal gas pressure as they cool, but explosions are rare. Bomb explosions are most often observed in 'bread-crust' type bombs.

Ribbon or cylindrical bombs form from highly to moderately fluid magma, ejected as irregular strings and blobs. The strings break up into small segments which fall to the ground intact and look like ribbons. Hence, the name "ribbon bombs". These bombs are circular or flattened in cross section, are fluted along their length, and have tabular vesicles.

Spherical bombs also form from high to moderately fluid magma. In the case of spherical bombs, surface tension plays a major role in pulling the ejecta into spheres.

Spindle, fusiform, or almond/rotational bombs are formed by the same processes as spherical bombs, though the major difference being the partial nature of the spherical shape. Spinning during flight leaves these bombs looking elongated or almond shaped; the spinning theory behind these bombs' development has also given them the name 'fusiform bombs'. Spindle bombs are characterised by longitudinal fluting, one side slightly smoother and broader than the other. This smooth side represents the underside of the bomb as it fell through the air.

Cow pie bombs are formed when highly fluid magma falls from moderate height; so the bombs do not solidify before impact (they are still liquid when they strike the ground). They consequently flatten or splash and form irregular roundish disks, which resemble cow-dung.

Bread-crust bombs are formed if the outside of the lava bombs solidifies during their flights. They may develop cracked outer surfaces as the interiors continue to expand.

Cored bombs are bombs that have rinds of lava enclosing a core of previously consolidated lava. The core consists of accessory fragments of an earlier eruption, accidental fragments of country rock or, in rare cases, bits of lava formed earlier during the same eruption.

Rock structures
The image at the right shows rock strata in Cafayate, Argentina, the subject of stratigraphy.

Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories.

Marginal marines
The marginal marine sequence on the right has been dated to the Middle Triassic.

Rock types
Usually rock types consist of sedimentary, metamorphic and igneous.

Meteorites
Def. a meteorite that is known to have originated on the Moon is called a lunar meteorite.

The meteorite called Allan Hills 81005 resembled some rocks brought back from the Moon by the Apollo program.

Yamato 791197 is another lunar meteorite.

About 134 lunar meteorites have been discovered so far (as of October, 2010), perhaps representing more than 50 separate meteorite falls (i.e., many of the stones are "paired" fragments of the same meteoroid). The total mass is more than 46 kg.

Meteorites have been found on the Moon.

Many of the meteorites that are found on Earth turn out to be from the Moon.

So far seifertite has only been found in Martian and lunar meteorites.

Eucrites
Def. an "achondritic meteoritic rock consisting chiefly of pigeonite and anorthite" is called a eucrite.

Igneous rocks
Def. "one of the major groups of rock that makes up the crust of the Earth; formed by the cooling of molten rock, either below the surface (intrusive) or on the surface (extrusive)" is called an igneous rock.

"An igneous rock is formed by the cooling and crystallization of molten rock."

Igneous "rocks [are divided] into two broad categories based on where the molten rock solidified."

The image on the left shows a collection of various igneous rocks: from top left to bottom right these are: granodiorite, andesite, syenite, gabbro, rhyolite, basalt, granite and an ignimbrite (a collective term for a special type of volcaniclastic sediment).

Andesites
Def. a "class of fine-grained intermediate [..] rock [...] containing mostly plagioclase feldspar" is called an andesite.

"Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende. At the lower end of the silica range, andesite lava may also contain olivine. Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several km in length. Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100° C."

Anorthosites
Def. a "phaneritic, [...] rock characterized by a predominance of plagioclase feldspar" is called an anorthosite.

Anorthosite on Earth can be divided into five types:
 * 1) Archean-age anorthosites
 * 2) Proterozoic anorthosite (also known as massif or massif-type anorthosite) – the most abundant type of anorthosite on Earth
 * 3) Layers within Layered Intrusions (e.g., Bushveld Igneous Complex and Stillwater igneous complex intrusions)
 * 4) Mid-ocean ridge and transform fault anorthosites
 * 5) Anorthosite xenoliths in other rocks (often granites, kimberlites, or basalts).

Plagioclase crystals are usually less dense than magma; so, as plagioclase crystallizes in a magma chamber, the plagioclase crystals float to the top, concentrating there.

Lunar anorthosites constitute the light-coloured areas of the Moon's surface and have been the subject of much research.

Proterozoic anorthosites were emplaced during the Proterozoic Eon (ca. 2,500–542 Ma), though most were emplaced between 1,800 and 1,000 Ma.

Large volumes of ultramafic rocks are not found in association with Proterozoic anorthosites.

Basalts
Def. a "hard mafic [...] rock of varied mineral content" is called a basalt.

"Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt's low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move > 20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns. Basaltic lava fountains and fissure eruptions, however, still form explosive fountains hundreds of meters tall. Common minerals in basalt include olivine, pyroxene, and plagioclase. Basalt is erupted at temperatures between 1100 to 1250° C."

"Basalt is the most common rock type in the Earth's crust (the outer 10 to 50 km). In fact, most of the ocean floor is made of basalt."

"Huge outpourings of lava called "flood basalts" are found on many continents. The Columbia River basalts, erupted 15 to 17 million years ago, cover most of southeastern Washington and regions of adjacent Oregon and Idaho."

"Basaltic magma is commonly produced by direct melting of the Earth's mantle, the region of the Earth below the outer crust. On continents, the mantle begins at depths of 30 to 50 km."

"Shield volcanoes, such as those that make up the Islands of Hawai`i, are composed almost entirely of basalt."

Carbonatites
Def. any "intrusive igneous rock having a majority of carbonate minerals" is called a carbonatite.

Dacites
Def. an "igneous, volcanic rock with a high iron content" is called a dacite.

"Dacite lava is most often light gray, but can be dark gray to black. Dacite lava consists of about 63 to 68 percent silica (SiO2). Common minerals include plagioclase feldspar, pyroxene, and amphibole. Dacite generally erupts at temperatures between 800 and 1000°C. It is one of the most common rock types associated with enormous Plinian-style eruptions. When relatively gas-poor dacite erupts onto a volcano's surface, it typically forms thick rounded lava flow in the shape of a dome."

"Even though it contains less silica than rhyolite, dacite can be even more viscous (resistant to flow) and just as dangerous as rhyolites. These characteristics are a result of the high crystal content of many dacites, within a relatively high-silica melt matrix. Dacite was erupted from Mount St. Helens 1980-86, Mount Pinatubo in 1991, and Mount Unzen 1991-1996."

Gabbros
Def. a dark, coarse-grained plutonic rock of crystalline texture, consisting mainly of pyroxene, plagioclase feldspar, and often olivine is called a gabbro.

Def. "a coarsely crystalline, igneous rock consisting of lamellar pyroxene and labradorite" is called a gabbro.

As with diamictites, rock definitions should be without regard to origin.

Granites
Def. a very hard, granular, crystalline, rock consisting mainly of quartz, mica, and feldspar is called a granite.

Def. a "group of igneous and plutonic rocks composed primarily of feldspar and quartz, usually [containing] one or more dark minerals, which may be mica, pyroxene, or amphibole" is called a granite.

Granodiorites
Def. a "rock similar to granite, but containing more plagioclase than potassium feldspar" is called a granodiorite.

Hawaiites
Def. an "olivine basalt intermediate between alkali olivine and mugearite" is called a hawaiite.

Monzogranites
Rochovce granite, composing the coring on the right, is a coarse-grained biotite monzogranite.

Peridotites
Def. a "rock consisting of small crystals of olivine, pyroxene and hornblende" is called a peridotite.

Rhyolites
Def. a rock "of felsic composition, with aphanitic to porphyritic texture" is called a rhyolite.

"Rhyolite is a light-colored rock with silica (SiO2) content greater than about 68 weight percent. Sodium and potassium oxides both can reach about 5 weight percent. Common mineral types include quartz, feldspar and biotite and are often found in a glassy matrix. Rhyolite is erupted at temperatures of 700 to 850° C."

"Rhyolite can look very different, depending on how it erupts. Explosive eruptions of rhyolite create pumice, which is white and full of bubbles. Effusive eruptions of rhyolite often produce obsidian, which is bubble-free and black."

"Some of the United States' largest and most active calderas formed during eruption of rhyolitic magmas (for example, Yellowstone in Wyoming, Long Valley in California and Valles in New Mexico)."

"Rhyolite often erupts explosively because its high silica content results in extremely high viscosity (resistance to flow), which hinders degassing. When bubbles form, they can cause the magma to explode, fragmenting the rock into pumice and tiny particles of volcanic ash."

Syenites
Def. an "igneous rock composed of feldspar and hornblende" is called a syenite.

On the left is a leucocratic variety of nepheline syenite from Sweden called särnaite.

Tonalites
Def. an "igneous, plutonic rock composed mainly of plagioclase" is called a tonalite.

Metamorphic rocks
] Def. "one of the major groups of rock that makes up the crust of the Earth; consists of pre-existing rock mass in which new minerals or textures are formed at higher temperatures and greater pressures than those present on the Earth's surface" is called a metamorphic rock.

Charnockite is any orthopyroxene-bearing quartz-feldspar rock formed at high temperature and pressure, commonly found in granulite facies metamorphic regions, sensu stricto as an endmember of the charnockite series.

Rocks of the charnockite series may be named by adding orthopyroxene to the normal igneous nomenclature (e.g. orthopyroxene-granite), but specific names are in widespread use such as norite, mangerite, enderbite, jotunite, farsundite, opdalite and charnockite (in the strict sense); equivalents of gabbro, monzonite, tonalite, monzodiorite, monzogranite, granodiorite and granite.

Amphibolites
Def. any "of a class of [...] rock composed mainly of amphibole with some quartz etc" is called an amphibolite.

On the left is foliated amphibolite, sample 81MW0005, a borehole sample from under Cape Cod in Massachusetts in USA. It is made of the minerals plagioclase (35%), hornblende (20%), biotite (20%), epidote (15%), quartz (9%), and trace oxides and sphene. Plagioclase is mostly fine grained and subhedral and occurs in the matrix. Fine-grained hornblende occurs as anhedral pleochroic green-tan crystals. Biotite is partly, but not entirely aligned in the foliation, suggesting that deformation took place before a secondary growth of biotite. Epidote is anhedral, and sometimes rimmed by biotite. Quartz occurs in 2 mm-thick aggregates and shows subgrain development.

Anthracites
Def. a "form of carbonized ancient plants; the hardest and cleanest-burning of all the coals; hard coal" is called anthracite.

Def. a coal of a hard variety that contains relatively pure carbon is called an anthracite.

Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92% and 98%.

Blueschists
Def. a "rock containing glaucophane" is called a blueschist. A metamorphic facies is a set of metamorphic mineral assemblages that were formed under similar pressures and temperatures. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram at right). Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and places in geological history of the area. The boundaries between facies (and corresponding areas on the temperature v. pressure graph), are wide, because they are gradational and approximate. The area on the graph corresponding to rock formation at the lowest values of temperature and pressure, is the range of formation of sedimentary rocks, as opposed to metamorphic rocks, in a process called diagenesis.

Blueschist is a metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius. The blue color of the rock comes from the presence of the mineral glaucophane. Blueschists are typically found within orogenic belts as terranes of lithology in faulted contact with greenschist or rarely eclogite facies rocks. ... Blueschist, as a rock type, is defined by the presence of the minerals glaucophane + ( lawsonite or epidote ) +/- jadeite +/- albite or chlorite +/- garnet +/- muscovite in a rock of roughly basaltic composition. Blueschist often has a lepidoblastic, nematoblastic or schistose rock microstructure defined primarily by chlorite, phengitic white mica, glaucophane, and other minerals with an elongate or platy shape. Grain size is rarely coarse, as mineral growth is retarded by the swiftness of the rock's metamorphic trajectory and perhaps more importantly, the low temperatures of metamorphism and in many cases the anhydrous state of the basalts. However, coarse varieties do occur. Blueschists may appear blue, black, gray, or blue-green in outcrop.

Gneisses
Def. a "rock having bands or veins, but not schistose" is called a gneiss.

Granulites
Def. "fine-grained [...] rock composed chiefly of feldspar, quartz, and garnets" is called a granulite.

Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism that are medium to coarse–grained and mainly composed of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure.

Hornfels
The hornfels shown on the right were formed from the heating of sandstones and siltstones by the Insskoy series of granite intrusions.

Maw sit sit
Maw sit sit, also known as jade-albite, is a gemstone found exclusively in northern Burma, first identified in 1963 by the late Swiss gemologist, Edward Gubelin, and was named after the village close to where it was first found in the foothills of the Himalayas.

Typically maw sit sit is green with distinctive dark-green to black veins, is technically a rock rather than a mineral, composed of several different minerals, including kosmochlor (also known as ureyite), varying amounts of chromium-enriched jadeite, and albite feldspar.

Maw sit sit can have a refractive index ranging from 1.52-1.68, and a hardness rating of 6 to 7 on the Mohs scale.

Marbles
On the right is a block of white marble.

The left shows Mississippian marble in Big Cottonwood Canyon, Wasatch Mountains, Utah.

Phyllites
A sample of a phyllite is on the right.

Quartzites
Def. "a [...] rock consisting of interlocking grains of quartz" is called a quartzite.

In a quartzite, fractures occur through the quartz grains. In a sedimentary rock composed of quartz grains, the rock fractures around the quartz grains.

Schists
At right is an image of schist.

Schist is a medium-grained metamorphic rock that shows well-developed schistosity. Schistosity is a thin layering of the rock produced by metamorphism (a foliation) that permits the rock to easily be split into flakes or slabs less than 5 to 10 mm thick. The mineral grains in a schist are typically from 0.25 to 2 mm in size and so are easily seen with a 10× hand lens. Typically, over half the mineral grains in a schist show a preferred orientation. Schists make up one of the three divisions of metamorphic rock by texture, with the other two divisions being gneiss, which has poorly developed schistosity and thicker layering, and granofels, which has no discernible schistosity.

Slates
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. Slate is frequently grey in color, especially when seen, en masse, covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green or cyan.

Def. a "fine-grained homogeneous [...] rock composed of clay or [...] ash which [...] cleaves easily into thin layers" is called a slate.

Sedimentary rocks
Def. "one of the major groups of rock that makes up the crust of the Earth; formed by the deposition of either the weathered remains of other rocks, the results of biological activity, or precipitation from solution" is called a sedimentary rock.

Aeolianites
Def. a "rock formed from dune sand, often calcareous" is called an aeolianite.

Argillites
Def. a "fine-grained sedimentary rock, intermediate between shale and slate, sometimes used as a building material" is called an argillite.

Arkoses
Def. a "sedimentary rock consisting of small fragments of feldspar and quartz similar to a coarse sand" is called an arkose.

Breccias
Def. a "rock composed of angular fragments in a matrix that may be of a similar or a different material" is called a breccia.

Calcarenites
Def. a "form of limestone (or dolomite) composed of sand sized grains derived from the erosion of older rocks" is called a calcarenite.

Conglomerates
Def. a "rock consisting of gravel or pebbles embedded in a matrix" is called a conglomerate.

Clastic rocks
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock, where a clast is a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering.

Claystones
Def. a "rock composed of fine, clay particles" is called a claystone.

Coals
Def. "a black rock formed from prehistoric plant remains, composed largely of carbon and burned as a fuel" is called a coal.

Def. a black coal having a relatively high volatile content is called a bituminous coal.

Diamictites
Def. "nonsorted, noncalcareous terrigenous deposits composed of sand and/or larger particles dispersed through a muddy matrix" are called diamictons.

Def. a lithified diamicton is called a diamictite.

"Such rocks have in common a mixed, ill-sorted, disperse-megaclastic lithology with a great to extreme range of size grades." The definitions of these rocks are "without regard to origin".

Def. a "sedimentary, calcareous conglomerate containing a mixture of particles; mixtite" is called a diamictite.

Greensands
Def. a "greenish sandstone containing glauconite" is called a greensand.

Greywackes
Def. a "hard dark sandstone with poorly sorted angular grains of quartz, feldspar, and small rock fragments in a compact, clay-fine matrix" is called a greywacke.

Gritstones
Def. a "form of sedimentary rock, similar to sandstone but coarser" is called a gritstone.

Lias
Def. a "stratigraphic group from the lower Jurassic period, consisting of thin layers of blue limestone [present in parts of southern England]" is called a lias.

Limestones
The middle Triassic layers of alpine limestone in the image on the right were deposited on the bottom of a shallow sea.

Lithification
Def. the "compaction and cementation of sediment into rock" is called lithification.

Def. a "subdivision of any stratigraphic unit that has characteristic lithologic features" is called a lithofacies.

Def. the "formation of sedimentary rock" is called lithogenesis.

Def. "an element that forms silicates or oxides and is concentrated in the minerals of the Earth's crust" is called a lithophile.

"The rocks are quartzose sandstones that were deposited on the eastern shore of ancient Lake Uinta, which existed during the Eocene. Some wisps and ribbons of dark-colored, magnetite-rich sand are present in the sandstone. The variety of chaotic rockforms at Fantasy Canyon are quite diverse - these cannot be explained by ordinary weathering and erosion. Close examination shows that erosion has acted upon differentially cemented sandstone. The sandstone has not undergone complete lithification and diagenesis - groundwater lobes have preferentially cemented portions of the sandstone, especially immediately adjacent to joint planes. The poorly-cemented sandstone was easily eroded & the better-cemented sandstone remains."

"Fantasy Canyon [is located] between Red Wash & Coyote Wash, Chapita Wells Gas Field, west-northwest of the town of Bonanza & south-southeast of the town of Vernal & east of the town of Ouray, northeastern Utah, USA."

Mudstones
Def. a "fine-grained sedimentary rock whose original constituents were clays or muds" is called a mudstone.

Oolites
Def. a "rock consisting of spherical grains within a mineral cortex accreted around a nucleus, often of quartz grains" is called an oolite.

Pelites
Def. a "sedimentary rock containing very fine particles" is called a pelites.

Phosphorites
Def. "a sedimentary rock rich in phosphate minerals such as apatite" is called a phosphorite.

Radiolarites
Def. "the sedimentary rock formed from" "radiolarian ooze" is called a radiolarite.

Sandstones
Def. a "sedimentary rock produced by the consolidation and compaction of sand, cemented with clay etc" is called a sandstone.

Sandstone classification by the Dott scheme uses the relative abundance of quartz, feldspar, and lithic framework grains and the abundance of a muddy matrix between the larger grains.

Shales
Def. a "fine-grained [...] rock of a thin, laminated, and often friable, structure" is called a shale.

Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility. Shale is the most common sedimentary rock.

The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock.

Siltstones
At the upper right is a small portion of the stratigraphic column between the Hatherton and MacKay glaciers in Antarctica. The top rock layer is a greyish red siltstone. The next downward is a greenish grey siltstone penetrated by sinuous tubes that may be roots or root-like structures. Underlaying this is "a zone of calcareous nodules."

"The Beacon Supergroup (Barrett, 1970) in the Transantarctic Mountains is largely a flat-lying, nonmarine sequence from Devonian or older to Jurassic in age. It consists of the Taylor Group (Devonian or older), a quartzose sandstone sequence, and the Victoria Group (Permian and Triassic), dominantly a coal-bearing sandstone-siltstone sequence (Harrington, 1965)."

"The Taylor Group comprises up to 1,450 m of quartzose sandstone, with smaller conglomerate, arkosic and shaly units [...]. [The] youngest Taylor Group unit [is] the Aztec Siltstone [of which the image at the right exhibits]."

Def. a "sedimentary rock whose composition is intermediate in grain size between the coarser sandstone and the finer mudstone" is called a siltstone.

Taconites
"This rock is widely spread over the whole length of the Mesabi, and being different from anything found elsewhere and peculiar to this horizon of the Taconic, has been called taconyte by the writer."

Taconite is a variety of iron formation, an iron-bearing (over 15% iron) sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate, of the Precambrian Biwabik Iron Formation of northeastern Minnesota, bearing a superficial resemblance to iron-bearing rocks from the Taconic Mountains of New York state.

Travertines
Def. "light, porous form of concretionary limestone (or calcite)" is called a travertine.

Turbidites
Def. "sea-bottom deposits formed by massive slope failures where rivers have deposited large deltas" are called turbidites.

"Turbidites [shown in the images] are sea-bottom deposits formed by massive slope failures where rivers have deposited large deltas. These slopes fail in response to earthquake shaking or excessive sedimentation load. The temporal correlation of turbidite occurrence for some deltas of the Pacific Northwest suggests that these deposits have been formed by earthquakes."

"Turbidites (interbedded with mudstones/siltstones) from the Ross Sandstone Formation Turbidite system of Namurian age in County Clare, Western Ireland. The sandstone beds were formed in a deep basin by turbidites coming from a delta area."

Hadean
Contrast-enhanced true color satellite image (Landsat 5) of the Jack Hills in Western Australia. The rocks of the Jack Hills are very old (~ 3 Billion years) and belong to the so-called Yilgarn Craton. Yet some of these rocks, the Jack Hills conglomerate (actually a metaconglomerate) contain individual grains of zircon which are even older, more than 4 Billion years old. They are used by geoscientists to reconstruct the very early history of the earth.

Def.
 * 1) "the geologic eon from about 4,600 to 3,800 million years ago; marked by the formation of the solar system, a stable Earth-Moon orbit and the first rocks" or
 * 2) the "eon before 4,000 Ma"

is called the Hadean.

"[U]ranium-lead dating [has been conducted] on fragments of the mineral zircon extracted from Apollo 14 lunar samples. The pieces of zircon were minuscule — no bigger than a grain of sand."

"Size doesn't matter, they record amazing information nonetheless! The moon holds "so much magic ... the key to understand how our beautiful Earth formed and evolved."

More "zircons from Apollo 14 samples [from the moon's Fra Mauro highlands collected in February 1971 are being studied], but [are not expected] to change [the] estimate of 4.51 billion years for the moon's age, possibly 4.52 billion years at the most."

"It would be more a double-checking than anything else."

Regardless "of how the moon came to be — one big strike at Earth, many smaller ones or even none at all — you still end up at the end solidifying the moon as we know it today."

"We finally pinned down a minimum age for the moon formation, regardless of how it formed."