In Old World archaeology, Mesolithic is the period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic is used synonymously for outside northern Europe, for the corresponding period in the Levant and Caucasus; the Mesolithic has different time spans in different parts of Eurasia. It refers to the final period of hunter-gatherer cultures in Europe and Western Asia, between the end of the Last Glacial Maximum and the Neolithic Revolution. In Europe it spans 15,000 to 5,000 BP; the term is less used of areas further east, not at all beyond Eurasia and North Africa. The type of culture associated with the Mesolithic varies between areas, but it is associated with a decline in the group hunting of large animals in favour of a broader hunter-gatherer way of life, the development of more sophisticated and smaller lithic tools and weapons than the heavy chipped equivalents typical of the Paleolithic. Depending on the region, some use of pottery and textiles may be found in sites allocated to the Mesolithic, but indications of agriculture are taken as marking transition into the Neolithic.
The more permanent settlements tend to be close to the sea or inland waters offering a good supply of food. Mesolithic societies are not seen as complex, burials are simple; the terms "Paleolithic" and "Neolithic" were introduced by John Lubbock in his work Pre-historic Times in 1865. The additional "Mesolithic" category was added as an intermediate category by Hodder Westropp in 1866. Westropp's suggestion was controversial. A British school led by John Evans denied any need for an intermediate: the ages blended together like the colors of a rainbow, he said. A European school led by Louis Laurent Gabriel de Mortillet asserted that there was a gap between the earlier and later. Edouard Piette claimed to have filled the gap with his naming of the Azilian Culture. Knut Stjerna offered an alternative in the "Epipaleolithic", suggesting a final phase of the Paleolithic rather than an intermediate age in its own right inserted between the Paleolithic and Neolithic. By the time of Vere Gordon Childe's work, The Dawn of Europe, which affirms the Mesolithic, sufficient data had been collected to determine that a transitional period between the Paleolithic and the Neolithic was indeed a useful concept.
However, the terms "Mesolithic" and "Epipalaeolitic" remain in competition, with varying conventions of usage. In the archaeology of Northern Europe, for example for archaeological sites in Great Britain, Scandinavia and Russia, the term "Mesolithic" is always used. In the archaeology of other areas, the term "Epipaleolithic" may be preferred by most authors, or there may be divergences between authors over which term to use or what meaning to assign to each. In the New World, neither term is used. "Epipaleolithic" is sometimes used alongside "Mesolithic" for the final end of the Upper Paleolithic followed by the Mesolithic. As "Mesolithic" suggests an intermediate period, followed by the Neolithic, some authors prefer the term "Epipaleolithic" for hunter-gatherer cultures who are not succeeded by agricultural traditions, reserving "Mesolithic" for cultures who are succeeded by the Neolithic Revolution, such as the Natufian culture. Other authors use "Mesolithic" as a generic term for post-LGM hunter-gatherer cultures, whether they are transitional towards agriculture or not.
In addition, terminology appears to differ between archaeological sub-disciplines, with "Mesolithic" being used in European archaeology, while "Epipalaeolithic" is more common in Near Eastern archaeology. The Balkan Mesolithic begins around 15,000 years ago. In Western Europe, the Early Mesolithic, or Azilian, begins about 14,000 years ago, in the Franco-Cantabrian region of northern Spain and southern France. In other parts of Europe, the Mesolithic begins by 11,500 years ago, it ends with the introduction of farming, depending on the region between c. 8,500 and 5,500 years ago. Regions that experienced greater environmental effects as the last glacial period ended have a much more apparent Mesolithic era, lasting millennia. In northern Europe, for example, societies were able to live well on rich food supplies from the marshlands created by the warmer climate; such conditions produced distinctive human behaviors that are preserved in the material record, such as the Maglemosian and Azilian cultures.
Such conditions delayed the coming of the Neolithic until some 5,500 BP in northern Europe. The type of stone toolkit remains one of the most diagnostic features: the Mesolithic used a microlithic technology – composite devices manufactured with Mode V chipped stone tools, while the Paleolithic had utilized Modes I–IV. In some areas, such as Ireland, parts of Portugal, the Isle of Man and the Tyrrhenian Islands, a macrolithic technology was used in the Mesolithic. In the Neolithic, the microlithic technology was replaced by a macrolithic technology, with an increased use of polished stone tools such as stone axes. There is some evidence for the beginning of construction at sites with a ritual or astronomical significance, including Stonehenge, with a short row of large post holes aligned east-west, a possible "lunar calendar" at Warren Field in Scotland, with pits of post holes of varying sizes, thought to reflect the lunar phases. Both are dated to before c. 9,000 BP. As the "Neolithic package" (including farming, polished stone axes, timber longhouses and pot
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
The Vedda are a minority indigenous group of people in Sri Lanka who, among other self-identified native communities such as Coast Veddas, Anuradhapura Veddas and Bintenne Veddas, are accorded indigenous status. The Veddha minority in Sri Lanka is in threat of becoming extinct. Most speak Sinhala instead owing to near-extinction of their indigenous languages, it has been hypothesized that the Vedda were the earliest inhabitants of Sri Lanka and have lived in the island before the arrival of Vijaya and his clan from India. According to the 5th-century genesis chronicle of the Sinhalese people, the Mahavamsa, the Vedda are descended from Prince Vijaya, the founding father of the nation, who originated from Eastern India, through Kuveni, a woman of the indigenous Yakkha whom he married; the Mahavansa relates that following the repudiation of Kuveni by Vijaya, in favour of a Kshatriya-caste princess from Pandya, their two children, a boy and a girl, departed to the region of Sumanakuta, where they multiplied, giving rise to the Veddas.
Anthropologists such as Charles Gabriel Seligman believed the Veddas to be identical to the Yakkha. Veddas are mentioned in Robert Knox's history of his captivity by the King of Kandy in the 17th century. Knox described them as "wild men", but said there was a "tamer sort", that the latter sometimes served in the king's army; the Ratnapura District, part of the Sabaragamuwa Province, is known to have been inhabited by the Veddas in the distant past. This has been shown by scholars like Nandadeva Wijesekera; the name Sabaragamuwa is believed to have meant the village of the Sabaras or "forest barbarians". Place-names such as Vedda-gala, Vedda-ela and Vedi-Kanda in the Ratnapura District bear testimony to this; as Wijesekera observes, a strong Vedda element is discernible in the population of Vedda-gala and its environs. Ethonyms of Vedda include Vadda, Veddah and Vaddo. "Vedda" stems from Tamil word Vēdu meaning hunting. The original language of the Veddas is the Vedda language, which today is used by the interior Veddas of Dambana.
Communities such as Coast Veddas and Anuradhapura Veddas, who do not identify themselves as Veddas use Vedda language for communication during hunting and or for religious chants. When a systematic field study was conducted in 1959 it was determined that the language was confined to the older generation of Veddas from Dambana. In the 1990s, self-identifying Veddas knew few words and phrases in the Vedda language, but there were individuals who knew the language comprehensively. There was considerable debate among linguists as to whether Vedda is a dialect of Sinhala or an independent language. Studies indicate that it diverged from its parent stock in the 10th century and became a Creole and a stable independent language by the 13th century, under the influence of Sinhala; the parent Vedda language is of unknown genetic origins, while Sinhala is of the Indo-Aryan branch of Indo-European languages. Phonologically it is distinguished from Sinhala by the higher frequency of palatal sounds C and J.
The effect is heightened by the addition of inanimate suffixes. Vedda language word class is morphologically divided into nouns and variables with unique gender distinctions inanimate nouns. Per its Creole tradition, it has reduced and simplified many forms of Sinhala such as second person pronouns and denotations of negative meanings. Instead of borrowing new words from Sinhala, Vedda created combinations of words from a limited lexical stock. Vedda maintains many archaic Sinhala terms prior to the 10th to 12th centuries, as a relict of its close contact with Sinhala. Vedda retains a number of unique words that cannot be derived from Sinhala. Sinhala has borrowed from the original Vedda language and grammatical structures, differentiating it from its related Indo-Aryan languages. Vedda has exerted a substratum influence in the formation of Sinhala. Veddas that have adopted Sinhala are found in the southeastern part of the country in the vicinity of Bintenne in Uva Province. There are Veddas that have adopted Sinhala who live in Anuradhapura District in the North Central Province.
Another group termed East Coast Veddas, is found in coastal areas of the Eastern Province, between Batticaloa and Trincomalee. These Veddas have adopted Tamil as their mother tongue; the parent of Vedda language is of unknown linguistic origin, is considered a linguistic isolate. Early linguists and observers of the language considered it to be either a separate language or a dialect of Sinhala; the chief proponent of the dialect theory was Wilhelm Geiger, but he contradicted himself by claiming that Vedda was a relexified aboriginal language. Veddas consider the Vedda language to be distinct from Sinhala and use it as an ethnic marker to differentiate them from Sinhalese people; the original religion of Veddas is animism. The Sinhalized interior Veddahs follow a mix of animism and nominal Buddhism. One of the most distinctive features of Vedda religion is the worship of dead ancestors, who are called "nae yaku" among the Sinhala-speaking Veddas and are invoked for the game and yams. There are peculiar deities unique to Veddas, such as "Kande Yakka".
Veddas, along with the Island's Buddhist and Muslim communities, venerate the temple complex situated at Kataragama, showing the sync
A primate is a eutherian mammal constituting the taxonomic order Primates. Primates arose 85–55 million years ago from small terrestrial mammals, which adapted to living in the trees of tropical forests: many primate characteristics represent adaptations to life in this challenging environment, including large brains, visual acuity, color vision, altered shoulder girdle, dexterous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs 30 g, to the eastern gorilla, weighing over 200 kg. There are 190 -- 448 species of living primates, depending on. New primate species continue to be discovered: over 25 species were described in the first decade of the 2000s, eleven since 2010. Primates are divided into two distinct suborders; the first is the strepsirrhines - lemurs and lorisids. The second is haplorhines - the "dry-nosed" primates - tarsier and ape clades, the last of these including humans. Simians are monkeys and apes, cladistically including: the catarrhines consisting of the Old World monkeys and apes.
Forty million years ago, simians from Africa migrated to South America by drifting on debris, gave rise to the New World monkeys. Twenty five million years ago the remaining Old World simians split into Old World monkeys. Common names for the simians are the baboons, macaques and great apes. Primates have large brains compared to other mammals, as well as an increased reliance on visual acuity at the expense of the sense of smell, the dominant sensory system in most mammals; these features are more developed in monkeys and apes, noticeably less so in lorises and lemurs. Some primates are trichromats, with three independent channels for conveying color information. Except for apes, primates have tails. Most primates have opposable thumbs. Many species are sexually dimorphic. Primates have slower rates of development than other sized mammals, reach maturity and have longer lifespans. Depending on the species, adults may live in solitude, in mated pairs, or in groups of up to hundreds of members; some primates, including gorillas and baboons, are terrestrial rather than arboreal, but all species have adaptations for climbing trees.
Arboreal locomotion techniques used include leaping from tree to tree and swinging between branches of trees. Primates are among the most social of animals, forming pairs or family groups, uni-male harems, multi-male/multi-female groups. Non-human primates have at four types of social systems, many defined by the amount of movement by adolescent females between groups. Most primate species remain at least arboreal: the exceptions are some great apes and humans, who left the trees for the ground and now inhabit every continent. Close interactions between humans and non-human primates can create opportunities for the transmission of zoonotic diseases virus diseases, including herpes, ebola and hepatitis. Thousands of non-human primates are used in research around the world because of their psychological and physiological similarity to humans. About 60% of primate species are threatened with extinction. Common threats include deforestation, forest fragmentation, monkey drives, primate hunting for use in medicines, as pets, for food.
Large-scale tropical forest clearing for agriculture most threatens primates. The English name "primates" is derived from Old French or French primat, from a noun use of Latin primat-, from primus; the name was given by Carl Linnaeus. The relationships among the different groups of primates were not understood until recently, so the used terms are somewhat confused. For example, "ape" has been used either as an alternative for "monkey" or for any tailless human-like primate. Sir Wilfrid Le Gros Clark was one of the primatologists who developed the idea of trends in primate evolution and the methodology of arranging the living members of an order into an "ascending series" leading to humans. Used names for groups of primates such as "prosimians", "monkeys", "lesser apes", "great apes" reflect this methodology. According to our current understanding of the evolutionary history of the primates, several of these groups are paraphyletic: a paraphyletic group is one which does not include all the descendants of the group's common ancestor.
In contrast with Clark's methodology, modern classifications identify only those groupings that are monophyletic. The cladogram below shows one possible classification sequence of the living primates: groups that use common names are shown on the right. All groups with scientific names are monophyletic, the sequence of scientific classification reflects the evolution
Archaeology, or archeology, is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, biofacts or ecofacts and cultural landscapes. Archaeology can be considered a branch of the humanities. In North America archaeology is a sub-field of anthropology, while in Europe it is viewed as either a discipline in its own right or a sub-field of other disciplines. Archaeologists study human prehistory and history, from the development of the first stone tools at Lomekwi in East Africa 3.3 million years ago up until recent decades. Archaeology is distinct from palaeontology, the study of fossil remains, it is important for learning about prehistoric societies, for whom there may be no written records to study. Prehistory includes over 99% of the human past, from the Paleolithic until the advent of literacy in societies across the world. Archaeology has various goals, which range from understanding culture history to reconstructing past lifeways to documenting and explaining changes in human societies through time.
The discipline involves surveying and analysis of data collected to learn more about the past. In broad scope, archaeology relies on cross-disciplinary research, it draws upon anthropology, art history, ethnology, geology, literary history, semiology, textual criticism, information sciences, statistics, paleography, paleontology and paleobotany. Archaeology developed out of antiquarianism in Europe during the 19th century, has since become a discipline practiced across the world. Archaeology has been used by nation-states to create particular visions of the past. Since its early development, various specific sub-disciplines of archaeology have developed, including maritime archaeology, feminist archaeology and archaeoastronomy, numerous different scientific techniques have been developed to aid archaeological investigation. Nonetheless, archaeologists face many problems, such as dealing with pseudoarchaeology, the looting of artifacts, a lack of public interest, opposition to the excavation of human remains.
The science of archaeology grew out of the older multi-disciplinary study known as antiquarianism. Antiquarians studied history with particular attention to ancient artifacts and manuscripts, as well as historical sites. Antiquarianism focused on the empirical evidence that existed for the understanding of the past, encapsulated in the motto of the 18th-century antiquary, Sir Richard Colt Hoare, "We speak from facts not theory". Tentative steps towards the systematization of archaeology as a science took place during the Enlightenment era in Europe in the 17th and 18th centuries. In Europe, philosophical interest in the remains of Greco-Roman civilization and the rediscovery of classical culture began in the late Middle Age. Flavio Biondo, an Italian Renaissance humanist historian, created a systematic guide to the ruins and topography of ancient Rome in the early 15th century, for which he has been called an early founder of archaeology. Antiquarians of the 16th century, including John Leland and William Camden, conducted surveys of the English countryside, drawing and interpreting the monuments that they encountered.
One of the first sites to undergo archaeological excavation was Stonehenge and other megalithic monuments in England. John Aubrey was a pioneer archaeologist who recorded numerous megalithic and other field monuments in southern England, he was ahead of his time in the analysis of his findings. He attempted to chart the chronological stylistic evolution of handwriting, medieval architecture and shield-shapes. Excavations were carried out by the Spanish military engineer Roque Joaquín de Alcubierre in the ancient towns of Pompeii and Herculaneum, both of, covered by ash during the Eruption of Mount Vesuvius in AD 79; these excavations began in 1748 in Pompeii, while in Herculaneum they began in 1738. The discovery of entire towns, complete with utensils and human shapes, as well the unearthing of frescos, had a big impact throughout Europe. However, prior to the development of modern techniques, excavations tended to be haphazard; the father of archaeological excavation was William Cunnington. He undertook excavations in Wiltshire from around 1798.
Cunnington made meticulous recordings of Neolithic and Bronze Age barrows, the terms he used to categorize and describe them are still used by archaeologists today. One of the major achievements of 19th-century archaeology was the development of stratigraphy; the idea of overlapping strata tracing back to successive periods was borrowed from the new geological and paleontological work of scholars like William Smith, James Hutton and Charles Lyell. The application of stratigraphy to archaeology first took place with the excavations of prehistorical and Bronze Age sites. In the third and fourth decades of the 19th-century, archaeologists like Jacques Boucher de Perthes and Christian Jürgensen Thomsen began to put the artifacts they had found in chronological order. A major figure in the development of archaeology into a rigorous science was the army officer and ethnologist, Augustus Pitt Rivers, who began excavations on his land in England in the 1880s, his approach was methodical by the standards of the time, he is regarded as the first scientific archaeologist.
He arranged his artifacts by type or "typologically, within types by date or "chronologically"
A microlith is a small stone tool made of flint or chert and a centimetre or so in length and half a centimetre wide. They were made by humans from around 35,000 to 3,000 years ago, across Europe, Africa and Australia; the microliths were used in spear arrowheads. Microliths are produced from either a small blade or a larger blade-like piece of flint by abrupt or truncated retouching, which leaves a typical piece of waste, called a microburin; the microliths themselves are sufficiently worked so as to be distinguishable from workshop waste or accidents. Two families of microliths are defined: laminar and geometric. An assemblage of microliths can be used to date an archeological site. Laminar microliths are associated with the end of the Upper Paleolithic and the beginning of the Epipaleolithic era. Geometric microliths may be trapezoid or lunate. Microlith production declined following the introduction of agriculture but continued in cultures with a rooted hunting tradition. Regardless of type, microliths were used to form the points of hunting weapons, such as spears and arrows, other artifacts and are found throughout Africa and Europe.
They were utilised with wood, bone and fiber to form a composite tool or weapon, traces of wood to which microliths were attached have been found in Sweden and England. An average of between six and eighteen microliths may have been used in one spear or harpoon, but only one or two in an arrow. Laminar microliths date from at least the Gravettian culture or the start of the Upper Paleolithic era, they are found all through the Mesolithic and Neolithic eras. "Noailles" burins and micro-gravettes indicate that the production of microliths had started in the Gravettian culture. This style of flint working flourished during the Magdalenian period and persisted in numerous Epipaleolithic traditions all around the Mediterranean basin; these microliths are larger than the geometric microliths that followed and were made from the flakes of flint obtained ad hoc from a small nucleus or from a depleted nucleus of flint. They were produced either by the application of a variable pressure. There are three basic types of laminar microlith.
The truncated blade type can be divided into a number of sub-types depending on the position of the truncation and according to its form, for example, concave or convex. "Raclette scrapers" are notable for their particular form, being blades or flakes whose edges have been retouched until they are semicircular or shapeless. Raclettes are indefinite cultural indicators, as they appear from the Upper Paleolithic through to the Neolithic. Backed edge blades have one of the edges a side one, rounded or chamfered by abrupt retouching. There are fewer types of these blades, may be divided into those where the entire edge is rounded and those where only a part is rounded, or straight, they are fundamental in the blade-forming processes, from them, innumerable other types were developed. Dufour bladelets are up to three centimeters in length, finely shaped with a curved profile whose retouches are semi-abrupt and which characterize a particular phase of the Aurignacian period. Solutrean backed edge blades display pronounced and abrupt retouching, so that they are long and narrow and, although rare, characterize certain phases of the Solutrean period.
Ouchtata bladelets are similar to the others, except that the retouched back is not uniform but irregular. The Ibero-Maurusian and the Montbani bladelet, with a partial and irregular lateral retouching, is characteristic of the Italian Tardenoisian; these are sharp bladelets formed by abrupt retouching. There are a huge number of regional varieties of these microliths, nearly all of which are hard to distinguish without knowing the archaeological context in which they appear; the following is a small selection. Omitted are the foliaceous tips, which are characterized by a covering retouch and which constitute a group apart; the Châtelperrón point is not a true microlith. Its antiquity and its short, curved blade edge make it the antecedent of many laminar microliths; the Micro-gravette or Gravette micro point is a microlith version of the Gravette point and is a narrow bladelet with an abrupt retouch, which gives it a characteristically sharp edge when compared to other types. The Azilian point links the Magdalenian microlith points with those from the western Epipaleolithic.
They can be identified by a invasive retouching. The Ahrensburgian point is a peripheral paleolithic or western Epipaleolithic piece, but with a more specific morphology, as it is formed on a blade, is obliquely truncated and has a small tongue that served as a haft on a spear point; the next group contains a number of points from the Middle East characterized as cultural markers. The Emireh point from the Upper Paleolithic is the same as one found in Châtelperrón, to be contemporary, although they are shorter and appear to be fashioned from a blade and not a bladelet; the El-Wad point is from the end of the Upper Paleolithic from the same area, made from a long, thin bladelet. The El-Khiam point has been ident
Chert is a hard, fine-grained sedimentary rock composed of crystals of quartz that are small. Quartz is the mineral form of silicon dioxide. Chert is of biological origin but may occur inorganically as a chemical precipitate or a diagenetic replacement. Geologists use chert as a generic name for any type of cryptocrystalline quartz. Chert is of biological origin, being the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, which contains the silicon skeletal remains of diatoms, silicoflagellates, radiolarians. Depending on its origin, it can contain small macrofossils, or both, it varies in color, but most manifests as gray, grayish brown and light green to rusty red. Chert occurs in carbonate rocks as oval to irregular nodules in greensand, limestone and dolostone formations as a replacement mineral, where it is formed as a result of some type of diagenesis. Where it occurs in chalk or marl, it is called flint, it occurs in thin beds, when it is a primary deposit.
Thick beds of chert occur in deep marine deposits. These thickly bedded cherts include the novaculite of the Ouachita Mountains of Arkansas and similar occurrences in Texas and South Carolina in the United States; the banded iron formations of Precambrian age are composed of alternating layers of chert and iron oxides. Chert occurs in diatomaceous deposits and is known as diatomaceous chert. Diatomaceous chert consists of beds and lenses of diatomite which were converted during diagenesis into dense, hard chert. Beds of marine diatomaceous chert comprising strata several hundred meters thick have been reported from sedimentary sequences such as the Miocene Monterey Formation of California and occur in rocks as old as the Cretaceous. In petrology the term "chert" is used to refer to all rocks composed of microcrystalline, cryptocrystalline and microfibrous quartz; the term does not include quartzite. Chalcedony is a microfibrous variety of quartz. Speaking, the term "flint" is reserved for varieties of chert which occur in chalk and marly limestone formations.
Among non-geologists, the distinction between "flint" and "chert" is one of quality – chert being lower quality than flint. This usage of the terminology is prevalent in North America and is caused by early immigrants who brought the terms from England where most true flint was indeed of better quality than "common chert". Among petrologists, chalcedony is sometimes considered separately from chert due to its fibrous structure. Since many cherts contain both microcrystalline and microfibrous quartz, it is sometimes difficult to classify a rock as chalcedony, thus its general inclusion as a variety of chert; the cryptocrystalline nature of chert, combined with its above average ability to resist weathering, recrystallization and metamorphism has made it an ideal rock for preservation of early life forms. For example: The 3.2 Ga chert of the Fig Tree Formation in the Barbeton Mountains between Swaziland and South Africa preserved non-colonial unicellular bacteria-like fossils. The Gunflint Chert of western Ontario preserves not only bacteria and cyanobacteria but organisms believed to be ammonia-consuming and some that resemble green algae and fungus-like organisms.
The Apex Chert of the Pilbara craton, Australia preserved eleven taxa of prokaryotes. The Bitter Springs Formation of the Amadeus Basin, Central Australia, preserves 850 Ma cyanobacteria and algae; the Rhynie chert of Scotland has remains of a Devonian land flora and fauna with preservation so perfect that it allows cellular studies of the fossils. In prehistoric times, chert was used as a raw material for the construction of stone tools. Like obsidian, as well as some rhyolites, felsites and other tool stones used in lithic reduction, chert fractures in a Hertzian cone when struck with sufficient force; this results in 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 removing a full or partial cone; the partial Hertzian cones produced during lithic reduction are called flakes, exhibit features characteristic of this sort of breakage, including striking platforms, bulbs of force, eraillures, which are small secondary flakes detached from the flake's bulb of force.
When a chert stone is struck against an iron-bearing surface sparks result. This makes chert an excellent tool for starting fires, both flint and common chert were used in various types of fire-starting tools, such as tinderboxes, throughout history. A primary historic use of common chert and flint was for flintlock firearms, in which the chert striking a metal plate produces a spark that ignites a small reservoir containing black powder, discharging the firearm. Cherts are subject to problems. Weathered chert develops surface pop-outs when used in concrete that undergoes freezing and thawing because of the high porosity of weathered cher