Flint, a peculiar amorphous variety of nearly pure quartz, found in chalk, in nodular masses or in layers, sometimes forming beds of such extent as to be used for building, as in the counties of Kent, Suffolk, and Norfolk, England. It is usually of a dark color from the presence of carbonaceous matter, supposed to be derived from animal remains; but some specimens are almost white and transparent. It breaks with a smooth conchoidal fracture, and very sharp edges may be formed upon it with a hammer; a quality which adapts it for being made into gun flints and arrow and spear heads. Its specific gravity is 2.59. Berzelius found in a specimen 0.117 per cent. of potash, 0.113 of lime, and traces of iron, alumina, and carbonaceous matter. According to Fuchs, the silica is partly soluble. It was formerly thought essential in the production of flint glass, but is now superseded by pure granular quartz or sand. It is still used in the manufacture of porcelain. Flint nodules constitute a peculiar feature in the chalk cliffs of the coast of England. They occur in horizontal layers scattered through the upper portion of the chalk formation, and in a few instances have been seen in vertical rows like pillars, at irregular distances, the nodules not being in contact either in the horizontal or vertical arrangement.

They commonly contain a nucleus of parts of marine fossils, such as are abundant in the chalk, as shells, sponges, echini, etc.; and they also present the forms of hollow geodes, their cavities lined with quartz crystals, iron pyrites, carbonate of iron, chalcedony, etc. - Flint is a common mineral production in the United States, but it is converted to no use. It abounds in the tertiary formations of the southern states, and is met with in the older rocks, even to the metamorphic quartz associated with the lowest stratified rocks. On the Lehigh mountain in Pennsylvania, at Leiber's Gap, is exposed in loose fragments in the soil a vast amount of flint rock, associated with cherty quartz in-crusted with chalcedony and mammillary and botryoidal crystallizations. In the woods west of the road 20 acres have been dug over by the Indians, to obtain the flint for arrow and spear heads. Piles of broken flint still lie uncovered by the sides of the excavations. The stone was highly prized by the Indians, and they worked it skilfully.