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Results for chalcedony:

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chalcedony

SYNONYMS OR RELATED TERMS: chalcedony
CATEGORY: geology
DEFINITION: A fine-grained hard stone, a variety of the silica mineral quartz. A form of chert, it is found in a variety of milky or grayish colors with distinctive parallel bands of contrasting color. In antiquity, chalcedony was the stone most used by the gem engraver for beads, seals, and sometimes as a substitute for flint. The agate, carnelian, jasper, and onyx are some of the varieties still cut and polished as ornamental stones.

opaline

SYNONYMS OR RELATED TERMS: chalcedony, chert, agate
CATEGORY: artifact
DEFINITION: A fine-grained siliceous rock type widely used for stone artifact manufacture in the southern African Stone Age

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agate

CATEGORY: geology
DEFINITION: A common semiprecious silica mineral and a variety of chalcedony that occurs in bands of various colors and is somewhat transparent. It is essentially a variety of quartz and was engraved in antiquity. Its name comes from a corruption of the word Achates, a river of Sicily, where Pliny said the mineral was first found.

Ambrona

CATEGORY: site
DEFINITION: A Lower Palaeolithic site in Soria, central Spain, first discovered before World War II. Ambrona probably dates 300,000-400,000 years ago, from the end of the Mindel glacial period. Its occupants hunted elephants, deer, and bovines though the horse was the most common animal in the area. There are stone hand axes, scrapers, and cleavers of the Acheulian type and similar to some African sites were made from chalcedony, quartzite, quartz, and limestone. Points were fashioned from young elephant tusks. Pieces of charcoal show that fire was used.

carnelian

SYNONYMS OR RELATED TERMS: cornelian
CATEGORY: geology
DEFINITION: A reddish brown semiprecious stone used for beads, seal stones, and jewelry in antiquity. The Indus Valley civilization, Greeks, and Romans valued the stone. It is a translucent variety of the silica mineral chalcedony. Carnelian is usually found in volcanic rocks, such as the Deccan Traps of western India. Engraved cornelians in rings and signets have offered information about manners and customs of ancient Greeks and Romans.

chert

SYNONYMS OR RELATED TERMS: hornstone, phthanite
CATEGORY: geology
DEFINITION: A coarse type of siliceous (silica) rock, a form of quartz, used for the manufacture of stone tools where flint was not available. It is of poorer quality than flint, formed from ancient ocean sediments and often has a semi-glassy finish. It is pinkish, white, brown, gray, or blue-gray in color. Flint, chert, and other siliceous rocks like obsidian are very hard, and produce a razor-sharp edge when properly flaked into tools. This crystalline form of the mineral silica is found as nodules in limestones. Varieties of chert are jasper, chalcedony, agate, flint, and novaculite. Chert and flint provided the main source of tools and weapons for Stone Age man.

cornelian

SYNONYMS OR RELATED TERMS: carnelian
CATEGORY: geology
DEFINITION: A translucent, semiprecious variety of the silica mineral chalcedony that owes its red to reddish brown color to hematite (iron oxide). Found in India, Brazil, Australia, Africa, and the Nile Valley. It was highly valued and used in rings and signets by the Greeks and Romans.

Don Noi

CATEGORY: site
DEFINITION: A Neolithic site in Thailand where stone-working was done near chalcedony quarries, dating to the 3rd millennium BC. Tools made included flaked adzes utilized flakes.

flint

SYNONYMS OR RELATED TERMS: chert, firestone
CATEGORY: geology
DEFINITION: A type of hard stone, often gray in color, found in rounded nodules and usually covered with a white incrustation. A member of the chalcedony group of water-bearing silica minerals, it was found from early use to fracture conchoidally and was ideal for making stone tools with sharp edges. It is chemically a quartz, but has a different microcrystalline structure. It can therefore be flaked readily in any direction and so shaped to many useful forms. It occurs widely, and where available was the basic material for man's tools until the advent of metal; it is commonest 'stone' of the Stone Age. The only types of stone preferred to it were obsidian and the tougher rocks used for ground tools in the Neolithic. The term is often used interchangeably with chert and also as a generic term denoting stone tools in the Old World. Nodules of flint occur commonly as seams in the upper and middle chalk of northwest Europe. During the Neolithic and Copper Age of Europe, flint workers recognized that flint from beds below ground were of superior quality to surface flint, especially for the manufacture of large tools such as axes. These beds were exploited by sinking shafts and then excavating galleries outwards. Flint mines are known from many areas of Europe and good examples occur in Poland (Krzemionki), Holland, Belgium (Spiennes) and England (Grimes Graves).