in ichthyology. See Cardium.

Shirl, in mineralogy, a species of stones of the garnet kind, belonging to the siliceous class. It is called Schoeler by Bergman, Lapis cornues crystallizatus by Wallerius, and Stannum crystallis columnaribus by Linnæus. It is hard and heavy, shooting into crystals of a prismatic figure, principally of a black or green colour. The name cockle for these kinds of stones is an old Cornish word; but is sometimes also applied to very different substances. The term shirl is adopted from the Germans. The English mineral name of call has also been used by some authors as synonymous with cockle, and these are even confounded together at the mines; but the call, definitively speaking, is the same with the substance called wolfram by the Germans.

The specific gravity of these stones is between 3000 and 3400, though always in proportion to their different solidities. They crack in the fire, and are very difficult to be fused; resisting both microcosmic salt and mineral alkali. They cannot totally be dissolved in aqua fortis; but the dissolved part is precipitated in a gelatinous form on the addition of an alkali. On a chemical analysis they are found to contain siliceous earth, argil, calcareous earth, and iron; which last is found in a much greater quantity when they are opaque than when transparent. According to Bergman, some contain 55 parts of siliceous earth, 39 of argillaceous, and six of pure calcareous earth; but some contain ten or twelve of magnesia. In Britain they are chiefly found in Cornwall, about the tin mines, and some fine crystallized kinds have been brought from Scotland. The varieties are,

1. The Schoeler martialis, or cockle mixed with iron. It is of a green colour, and found in most of the Swedish iron mines. It is coarse, and without any determinate figure.

2. The Spatulæ, or sparry cockle, is found in some places of a deep green colour; whence authors have called it the mother of emeralds. Its specific character is, that it always breaks in a cubic or rhomboidal form. In some parts of Sweden it is found of a pale green, white, or black colour, and of a brown colour in Westmoreland in England. It frequently occurs in the fealy lime-stones, and its colour changes from a deep green to white, in proportion as it contains more or less iron.

3. Fibrous cockle resembles threads of glass. These are either parallel, or like rays from a centre, in which last case it is called flamed cockle. Its colours are black, green, white, blackish green, and light green; all which are to be met with in Sweden. In Westfalenland it is found along with a steel-grained lead ore; and here the whole is called gran-ris-malm, or pine-ore, from its resemblance to the branches of that tree. Cronstedt observes, that the structure of this substance has caused it to be sometimes confounded with the asbestos, and that to this species belong most of the substances called imperfect asbestos. The flamed cockle, compared with the asbestos, is of a shining and angular surface, though this sometimes requires the aid of a magnifying glass to discover it; always somewhat transparent; and is pretty easily vitrified before the blowpipe, without being confused as the pure asbestos seem to be.

4. Crystallized cockle is found of black, deep-green, light-green, and reddish-brown in Sweden, and some other European countries. Near Basil in Switzerland it is found, though very rarely, a stone called toufflein, belonging to this variety. It is of a reddish-brown colour, and consists of two hexagonal crystals of cockle grown together in the form of a cross, which is worn by the Roman Catholics as an amulet, and called by them lapis crucifer, or the cross-stone. This form, however, is not peculiar to the cockle, for both Werner and Bergman mention crystals of mountain-crystal joined together in the same manner.

This variety was lately found by M. Fichtel on the Carpathian mountains, crystallized in prisms, and embodied in limestone. It effervesces slightly with acids, and contains 61.6 of silic, 21.6 of calcareous earth, 6.6 of argil, 5 of magnesia, 1.6 of iron, and three of water. The reddish-brown prismatic shirl from Vesuvius contains 48 of silic, 40 of argil, five of calx, one of magnesia, and five of iron. Other kinds, however, have afforded 50 per cent. of siliceous earth, 30 of argillaceous, one or two of magnesia, and 18 or 20 of iron. The white sort probably contains less iron, but all become reddish by calcination. Cronstedt informs us that he has heard of lead being melted out of a kind of cockle from Rodbeck's Eng at Umea in Lapland; and he also thinks it very probable, that some of the cockles found in the English tin mines may contain tin. Some crystals of cockle are more fusible than any sort of stone whatever; there are always glassy and limpid-transparent. Cockney mitransparent. The precise figure of the cockle, tho' always prismatical, is uncertain; that from Yxio, at Nya Kopparberg, is quadrangular; the French kind has nine sides or planes, and the taufflein is hexagonal.