FLINT is a calcedonic variety of silica found in the form of irregular concretionary nodules of varying size, chiefly in the Upper Chalk beds and in other similar lime-stone deposits. The mode in which flint originated is not altogether satisfactorily explained ; but as traces of some of the humbler marine organisms are almost invariably found in the nodules, it is assumed that the silicious matter wa3 partly derived from these organisms themselves, and that they formed nuclei around which soluble silica accumulated. From the prevalence of silicious spiculae of sponges in the nodules, it is affirmed by Dr Bowerbank that all flints had, for their primary nuclei, the silicious framework of the sponges which flourished in the depths of the sea during the Cretaceous epoch. Flints occur in the chalk in stratified order, and the various beds are possessed of a uniformly distinctive character. In some cases they are found in continuous layers, at other places they occur as isolated nodules. In the county of Norfolk, huge flints termed "potstones," of a pear-shaped outline, measuring as much as three feet in length by one foot across, are obtained ; and these are imbedded in the chalk at right angles to the horizontal layers of small flints. Flint is a compact homogeneous substance, externally coated with a white silicious coat, and frequently hollow in the centre. It has a dark steely grey, almost black, sometimes brownish colour; it is faintly translucent, and it breaks with a con-choidal or glassy fracture. In composition it consists of almost pure silica, partly in the crystalline or non-soluble quartzy form, and partly in the non-crystalline soluble state. It contains traces of lime, iron, and alumina, and when the proportion of lime present is large it passes into chert. When newly obtained from the pits the contained moisture of flint renders it easily flaked and other-wise worked, but after exposure to the air it becomes dry, hard, and intractable. From the earliest times flint has been employed as a fire-producer, by percussion with iron pyrites, and subsequently with a steel implement in the yet familiar form of "flint and steel." In classical authors occasional allusions are made to the use of flint knives ; and the employment of flint and steel to produce fire is very pointedly described by Virgil and other writers. Except to a trifling extent in the preparation of strike-a-light flints, the only form in which flint industry now con-tinues is in the fabrication of gun-flints, an occupation carried on at Brandon, and to a smaller extent at Icklingham, two villages in Suffolk. In 1876 there were 21 flint knappers in Brandon, and about 80,000 flints were sent away weekly, the greater proportion of which go to West Africa. The mining for flints is conducted by sinking a narrow pit into the chalk till the bed of suitable flints (the best are " floor-stones") is reached, and along this the miner drives a series of small galleries or burrows, carrying all the excavated material by hand to the surface. The knapper's tools consist of three simple forms of hammer and a chisel; and probably the only essential modification these tools have ever undergone consists in the substitution of metal for stone. The flint is first broken into convenient sized angular pieces, cubes of about 6 inches, called "quarters." The next operation, " flaking," consists in striking off, by means of carefully measured and well directed blows, flakes extending from end to end of the quarter, this process of flaking being continued till the quarter or core becomes too small to yield good flakes. The subsequent operation termed "knapping" consists in cutting or breaking the flakes transversely into the sizes required for gun-flints, each flake yielding two or three flints of different sizes. An expert flaker will make 7000 to 10,000 flakes in a day of twelve hours, and in the same time an average knapper will finish from flakes about 3000 gun-flints. Flint is also employed in building and for road metal. Calcined and powdered it is very much used in the manufacture of superior kinds of pottery. For the flint implements of primitive times, see ANTHROPOLOGY, vol. ii. p. 115. and ARCHAEOLOGY, vol. ii. p. 337.