Glass in nature

thumb|alt=A map of the world displaying the countries where opal is most commonly found; Australia, Ethiopia, Brazil, Mexico and the United States of America are highlighted.|Main opal producing countries

thumb|Kutkhiny Baty, a pumice rock formation outcrop located 4 km from the source of the Ozyornaya (Sea of Okhotsk)|Ozyornaya River (Lake Kurile), near the southern tip of the [[Kamchatka Peninsula, Russia]]

thumb|250px|Two splash-form tektites, molten terrestrial ejecta from a [[meteorite impact]]

thumb|upright=0.5|Fulgurite

material

Scoria or cinder (plural: scoriae) is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts. It is typically dark in color (brown, black or purplish-red), and basaltic or andesitic in composition. Scoria has relatively low density, as it is riddled with macroscopic ellipsoidal vesicles (gas bubbles), but in contrast to pumice, most scoria usually has a specific gravity greater than or at 1 and sinks or remains in place in water rather than float at the surface. However, some sco

thumb|An example of impactite on Earth (from Monturaqui impact crater, Chile) Impactite is rock created or modified by one or more impacts of a meteorite. Impactites are considered metamorphic rock, because their source materials were modified by the heat and pressure of the impact. On Earth, impactites consist primarily of modified terrestrial material, sometimes with pieces of the original meteorite.

Moldavite () is a forest green, olive green or blue greenish vitreous silica projectile glass formed by a meteorite impact in southern Germany (Nördlinger Ries Crater) that occurred about 15 million years ago. It is a type of tektite and a gemstone. Material ejected from the impact crater includes moldavite, which was strewn across parts of Germany, the Czech Republic and Austria.

right|thumb|250px|Palagonite layers at Moya Beach, Mayotte. Palagonite is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. Palagonite can also result from the interaction between water and basalt melt. The water flashes to steam on contact with the hot lava and the small fragments of lava react with the steam to form the light-colored palagonite tuff cones common in areas of basaltic eruptions in contact with water. An example is found in the pyroclastic cones of the Galapagos Islands. Charles Darwin recognized the origin of the

form of lava

Lechatelierite is silica glass, amorphous SiO2, non-crystalline mineraloid. It is named for Henry Louis Le Chatelier.

natural quartz glass, probably created by a meteorite impact

thumb|A pitchstone ridge of An Sgùrr (Eigg)|An Sgùrr in [[Eigg, Scotland]] Pitchstone is a dark coloured, glassy volcanic rock formed when felsic lava or magma cools quickly. Since it is a volcanic glass, pitchstone may have a conchoidal fracture. Pitchstones may also contain phenocrysts, in which case it is a form of vitrophyre. Pitchstone has a resinous lustre, or silky in some cases, and a variable composition. Its colour may be mottled, streaked, or uniform brown, red, green, gray, or black. It is an extrusive rock that is very resistant to erosion.

pieces of glass that have been naturally weathered by water

Small pieces of solidified lava drops

type of volcanic glass which resembles the algae

thumb|right|Aerodynamically shaped australite; the button shape is caused by ablation of molten glass in the atmosphere during reentry. Australites are tektites found in Australia. They are mostly dark or black, and have shapes including discs and bowls that are not seen in other tektites. NASA used the shape of "flanged button" australites in designing re-entry modules for the Apollo program in the 1960s.

describes the effects of shock-wave related deformation and heating during impact events

natural desert glass found in Tasmania

Maskelynite is a glassy material found in some meteorites and meteorite impact craters. Typical samples are similar in composition to plagioclase feldspar, and revert to that mineral when melted and recrystallized. It was named after British geologist M.H.N. Story-Maskelyne.