in natural history, a genus of stones belonging to the siliceous class. According to Cronstedt, all the opaque flints are called by this name whose texture resembles dry clay, and which cannot be any other way distinguished from flints, except that they are more easily melted; which perhaps may also proceed from a mixture of iron. The species are,

1. Pure jasper; which, Cronstedt informs us, cannot be decomposed by any means hitherto known; tho' Mr Kirwan says that it contains 75 per cent. of filex; 20 of argil, and about five of calx of iron. The specific gravity is from 2680 to 2778. It is found of different colours; viz. green with red dots from Egypt, called also the heliotrope, or blood stone; quite green from Bohemia; red from Italy, called there diaspro rosso, or yellow, called melites by the ancients; a name according to Pliny, of the same import with male coloris. It is also found red with yellow spots and veins, in Sicily, Spain, and near Constantinople, called by the Italians diaspro florido; or black from some places in Sweden, called by the Italians paragone antico.

2. Jaspis martialis, or finopole, containing iron. This is a dark red stone containing 18 or 20 per cent. of metal. Near Chemnitz, where it forms very considerable veins, as Brunnich informs us, it has frequently specks of marcasite, cubic lead ores, and blend. It has likewise so much gold as to be worth working; there is likewise a striped finopole of various colours. There are several varieties differing in the coarseness and fineness of their texture, as well as the shade of their colour; varying from a deep brown to a yellow. The last is attracted by the magnet after calcination.

Cronstedt observes that jasper, when fresh broken, so nearly resembles a bole of the same colour, that it can only be distinguished by its hardness. In the province of Dalarna in Sweden, it is found in a kind of hard sandstone; in other places it is found within such uncavous clefts as are usually met with in Cornish clay, red chalk, and other substances of that kind. There are likewise some jaspers that imbibe water; from whence, and other considerations, our author is of opinion that they have clay for their basis, notwithstanding their hardness. According to Magellan, it resists the blowpipe fire, and is only partially soluble with the mineral alkali; separating into small particles with effervescence; with borax or microcosmic salt it melts without any effervescence. Bergman, in his Sciagraphia, informs us, that it is composed of siliceous earth united to a clay very full of iron. The mineral acids have no effect upon it in a short time, but corrode it by some months immersion. On treating a small piece of green jasper with vitriolic acid, some crystals of alum and green vitriol were obtained; which shows that iron and clay are ingredients in its composition. M. Daubenton mentions 15 varieties of this substance. 1. Green, from Bohemia, Silea, Siberia, and the shores of the Caspian sea; which seems to be the pavonium of Aldrovandus. 2. The diaspro rosso, or red jasper; less common, and in smaller masses, than the green. 3. Yellow from Freyberg and Rochlitz; sometimes of a citron colour, and appearing as if composed of silky filaments; commonly called the silk jasper. 4. Brown from Dalecarlia in Finland and Sweden. 5. The violet from Siberia. 6. The black from Sweden, Saxony, and Finland. 7. The bluish-grey, a very rare species. 8. The milky white mentioned by Pliny, and found in Dalecarlia. 9. The variegated with green, red, and yellow clouds. 10. The blood stone, green with red specks, from Egypt, which was supposed to stop the blood. 11. The veined with various colours. Sometimes these veins have a distant resemblance to various letters, and then the jasper is named by the French jaspe grammaticque. Some of these found near Rochelle in France, on account of their curious variety in this respect, are named polygrammatiques. 12. The jasper with various coloured zones. 13. That called florito by the Italians; which has various colours mixed promiscuously without any order. 14. When the jasper has many colours together, it is then (very improperly) called universal. 15. When it contains some particles of agate, it is then called agatized jasper.