EARTHS. SILICEOUS. 52. Lydius. 
*59 
< 1 . l.YDIUS. Confifting of filica, a fmall quan- 
tity of limej magnefia, oxyde of iron and in- 
flammabk matter: hard, lightiOi, opake, com- 
paft, cinereous, black or gj-eenifli- black, flaty, 
of a common form, breaking into indeterminate 
fragments, dctaclied or conftituting mountains: 
not fufible per fe. 
Subopake, of a fpliutery fradlure, without intenxal 
luftre. 
Silex rupeftris. Sys(. nnt, xii. 3. p. 71. ». 15 ? 
jafpis unicolor nigra. 1. p. 299. n. i. g. 
Siliceous Shiftus, Kir’wan, miner . t. p. 306. 
Siliceous Shiftus. Schmeifser miner, i, p.iZJ. 
Keilellcheiferi Thomfon ehem, 3. p. 577. 
Found in various parts of Europe, in blocks and amorphous 
mall'es of various fizes, and very often in the beds of rivei-s: 
colour blackifli-grey or greenifi, often interfefted with veins 
of grey quartz or blood-rcd iron-ilone : fpcciSc gravity 
from 2,596. to 2,641. contains filica 75,00. lime 10,00. 
magnelia 4,18. iron 3,54. inflammable matter 5,02. 
IVefgUb- 
Of an even texture, lometimes approaching to the coit- 
choida!, fhining a little internally. 
Bafanite, Lydian ftone. Kirnian miverai. 307, 
Touchftone. Sehmei/ser mi’teral. i. />. 128. 
Lydian ftone. Tlbom/on ebem. p. 
Found in the river fmolas in L^d’a, and in various parts of 
Europe, detached or in maii'es, and is commonly interfefted 
by veins of quartz : colour dark greyifh-black ; its powder 
black : fpecific gravity 2,596. It is ufed as a touchftone to 
judge of the purity of metals. 
