Chert

Chert (IPA: /ˈtʃəː(r)t/) is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils. It varies greatly in color from white to black, but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively). Jasper is basically chert which owes its red color to iron(III) inclusions. Chert. ... Chert. ... For information on how to read IPA transcriptions of English words see here. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... A cryptocrystal is a rock whose texture is so finely crystalline—that is, made up of such minute crystals—that its crystalline nature is only vaguely revealed even in a thin section by transmitted polarized light. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ... Polished jasper pebble, one inch (2. ...

Chert outcrops as oval to irregular nodules in greensand, limestone, chalk, and dolostone formations as a replacement mineral, where it is formed as a result of diagenesis. It also occurs in thin beds, when it is a primary deposit. Thick beds of chert occur in deep geosynclinal deposits. These thickly bedded cherts include the novaculite of the Ouachita Mountains of Arkansas, Oklahoma, and similar occurrences in Texas in the United States. The banded iron formations of Precambrian age are composed of alternating layers of chert and iron oxides. Greensand is an olive-green coloured sandstone rock which found in narrow bands, particularly associated with bands of chalk and clay in northern and western Europe. ... Limey shale overlaid by limestone. ... The Needles, part of the extensive Southern England Chalk Formation. ... Dolostone is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite. ... In geology, diagenesis refers to all the chemical, physical, and biological changes undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering). ... Geosyncline refers to a thick pile of sedimentary rocks that were deposited in a deep marine basin and subsequently compressed, deformed, and uplifted into a mountain range with attendant volcanism and plutonism. ... Novaculite is a form of chert or flint found in the Ouachita Mountains of Arkansas and Oklahoma and in the Marathon Uplift of Texas. ... Ouachita Mountains The Ouachita Mountains are a mountain range located in west central Arkansas and east central Oklahoma. ... Official language(s) English Capital Little Rock Largest city Little Rock Area  Ranked 29th  - Total 53,179 sq mi (137,732 km²)  - Width 239 miles (385 km)  - Length 261 miles (420 km)  - % water 2. ... Official language(s) None Capital Oklahoma City Largest city Oklahoma City Area  Ranked 20th  - Total 69,960 sq mi (181,196 km²)  - Width 230 miles (370 km)  - Length 298 miles (480 km)  - % water 1. ... Official language(s) None See: Languages of Texas Capital Austin Largest city Houston Area  Ranked 2nd  - Total 268,581 sq mi (695,622 km²)  - Width 773 miles (1,244 km)  - Length 790 miles (1,270 km)  - % water 2. ... 2. ... The Precambrian (or Pre-Cambrian) is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon. ... Iron oxide pigment There are a number of iron oxides: Iron oxides Iron(II) oxide or ferrous oxide (FeO) The black-coloured powder in particular can cause explosions as it readily ignites. ...

Chert is generally considered to be less attractive and more common than flint, although the two materials are closely related. In geological terms flint and chert are the same, with the term flint referring to chert found in chalk. A flint nodule from the Onondaga limestone layer, Buffalo, New York. ... The Needles, part of the extensive Southern England Chalk Formation. ...

Chert and Precambrian fossils

The cryptocrystalline nature of chert, combined with its above average ability to resist weathering, recrystallisation and metamorphism has made it an ideal rock for preservation of early life forms^[1]. A cryptocrystal is a rock whose texture is so finely crystalline—that is, made up of such minute crystals—that its crystalline nature is only vaguely revealed even in a thin section by transmitted polarized light. ... Weathering is the process of breaking down of rocks, soils and their minerals through direct, or indirect contact with the atmosphere. ... Recrystallization is an essentially physical process that has meanings in chemistry and geology. ... Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ...

For example:

• The 3.2 billion year old chert of the Fig Tree Formation in the Barbeton Mountains between Swaziland and South Africa preserved non-colonial unicellular bacterial-like fossils^[2].
• The Gunflint Chert of western Ontario (1.9 to 2.3 BYA) preserves not only bacteria and cyanobacteria but also organisms believed to be ammonia-consuming and some that resemble green algae and fungus-like organisms^[3].
• The Apex Chert (3.4 BYA) of the Pilbara craton, Australia preserved eleven taxa of prokaryotes^[4].
• The Bitter Springs Formation of the Amadeus Basin, Central Australia, preserves 850 Ma old cyanobacteria and algae^[5].
• The Devonian Rhynie chert (400 MYA) of Scotland has the oldest remains of land flora, and the preservation is so perfect that it allows cellular studies of the fossils.

A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... The Gunflint chert is a sequence of banded iron formation rocks that are exposed in the Gunflint Range of northern Minnesota and western Ontario along the north shore of Lake Superior. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Orders The taxonomy of the Cyanobacteria is currently under revision. ... Divisions Chlorophyta Charophyta The Green algae (singular: Green Alga) are the large group of algae from which the embryophytes (higher plants) emerged. ... The Pilbara craton (the Pilbara province in northwest Western Australia), along with the Kaapvaal craton (the Kaapvaal province of South Africa) are the only remaining areas of pristine Archaean 3. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... Rhynie chert is the name for fossiliferous material from a uniquely well-preserved layer in one site near the village of Rhynie, Aberdeenshire, Scotland. ...

Chert and flint: archaeological and historical uses

In prehistoric times, chert was often used as a source material for stone tools. Like flint, obsidian, and chalcedony, as well as some rhyolites, felsites, quartzites and a few other tool stones used in lithic reduction, chert fractures in a Hertzian cone when struck with sufficient force. This results in conchoidal fractures, a characteristic of all minerals with no cleavage planes. In this kind of fracture, a cone of force propagates through the material from the point of impact, eventually removing a full or partial cone; this result is familiar to anyone who has seen what happens to a plate-glass window when struck by a small object, such as an airgun projectile. The partial Hertzian cones produced during lithic reduction are called flakes, and exhibit features characteristic of this sort of breakage, including striking platforms, bulbs of force, and occasionally eraillures, which are small secondary flakes detached from the flake's bulb of force. Ancient stone tools A stone tool is, in the most general sense, any tool made of stone. ... Obsidian from Lake County, Oregon Counterclockwise from top: obsidian, pumice and rhyolite (light color) Obsidian is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth (see glass transition temperature). ... Chalcedony knife, AD 1000-1200 Bloodstone redirects here. ... Rhyolite This page is about a volcanic rock. ... Felsite is a very fine to cryptocrystalline igneous rock that may or may not contain larger crystals, called phenocrysts, that are typical of many porphyritic igneous rocks. ... Quartzite Quartzite is a hard, metamorphic rock which was originally sandstone. ... In archaeology, a tool stone is a type of stone that is used to manufacture stone tools. ... Lithic reduction involves the use of a hard hammer percussor, such as a hammerstone, a soft hammer fabricator made of wood, bone or antler, or a wood or antler punch to detach lithic flakes from a lump of tool stone called a lithic core. ... A Hertzian cone is cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact, eventually removing a full or partial cone; this result is familiar to anyone who has seen what happens to a plate-glass window when struck by a small... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... In archaeology, a lithic flake is a thin, sharp fragment of stone that results from the process of lithic reduction. ... In lithic reduction, the striking platform is the point on the proximal portion of a lithic flake on which the detachment blow fell; this may be natural or prepared. ... In lithic analysis, a subdivision of archaeology, a bulb of applied force (also known as a bulb of percussion or simply bulb of force) is a defining characteristic of a lithic flake. ... In lithic analysis (a subdivision of archaeology), an eraillure is a small secondary flake removed from a lithic flakes bulb of force, which is a lump left on the dorsal surface of a flake after it is detached from a core of tool stone during the process of lithic...

When a chert stone is struck against steel, sparks result. This makes it an excellent tool for starting fires, and both flint and chert were used in various types of fire-starting tools, such as tinderboxes, throughout history. A primary historic use of chert was as flints for flintlock firearms, in which flint or chert striking a metal plate produces a spark that ignites a small reservoir containing black powder, discharging the firearm. Historically, a tinderbox is a small container containing flint, steel, and dry, finely-divided fibrous matter (such as straw), used together to help kindle a fire. ... Two flintlock pistols Flintlock is the general term for any firearm based on the flintlock mechanism. ... A firearm is a kinetic energy weapon that fires either a single or multiple projectiles propelled at high velocity by the gases produced by action of the rapid confined burning of a propellant. ... Black powder for sporting can be freely bought in Switzerland. ...

In some areas chert is ubiquitous as stream gravel and fieldstone and is currently used as construction material and road surfacing.

Chert has been used in late 19th-century and early 20th-century headstones or grave markers in Tennessee and other regions. Headstones in the Japanese Cemetry in Broome, Western Australia A cemetery in rural Spain A typical late 20th century headstone in the United States A headstone, tombstone or gravestone is a marker, normally carved from stone, placed over or next to the site of a burial. ...

See also

• Chalcedony
• Eolith
• Flint
• Obsidian
• List of minerals

Chalcedony knife, AD 1000-1200 Bloodstone redirects here. ... An eolith (from Greek eos, dawn, and lithos, stone) is a chipped flint nodule. ... A flint nodule from the Onondaga limestone layer, Buffalo, New York. ... Obsidian from Lake County, Oregon Counterclockwise from top: obsidian, pumice and rhyolite (light color) Obsidian is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth (see glass transition temperature). ... Gem animals. ...

References and external links

1. ^ THE EARLIEST LIFE: Annotated listing
2. ^ Fig Tree Formation of South Africa
3. ^ Gunflint chert
4. ^ BIOGENICITY OF MICROFOSSILS IN THE APEX CHERT
5. ^ Cyanobacertial fossils of the Bitter Springs Chert, UMCP Berkley

• Photo & note re: Fig Tree Formation
• Microphotographs of Fig Tree fossils
• Schopf, J.W. (1999) Cradle of Life: The Discovery of Earth's Earliest Fossils, Princeton University Press, 336 p. ISBN 0-691-00230-4

• An Archaeological Guide To Chert Types Of East-Central Illinois