13^ EARTHS, argillaceous. 39 . Opalus. 
with 'efFervefcence, and communicates no colour to jt : ef' 
fervefces (lightly with foda, and melts into a mafs fpottc 4 
with red: with microcofmic fait, it gives a pcarl-colouf 
globule; contains filica 53 alumina 20. potafs 18. dust 
of lime 5. oxydc of maneanefe 3. oxvde of iron 
Klaproth. 
39 ‘ QPAL.US. Confining of alumina, the greater 
proportion of filica, with a little oxyde ot iron, 
and generally fome carbonate of magnefia ani-1 
carbonate of lime : hardifii, fhining, haidly ever 
opake, of a conchoidal texture, light, breaking 
into indeterminate fragments, parafitical, gene- 
rally of a common form, cafily cracking into 
clefts: melting with the greateft difficulty. 
flydropha- Somewhat opake, becoming tranfparent and changing it* 
colour in liquids, adhering to the tongue. 
Achates unguium coiore. Syst. nat. xii. 3./1. 69, ». 6. d. 
Achates, &c. Wall fyst. min. p. h. Zl. 
Hydrophane. Kiriuan mineral. I. p. 295. 
Oculus mundi. Htdrophan. Schnmfser mineral, i. p. 141, 
Hydrophane, Oculus mundi, ‘Ihomfon chem. i- p. ^zi. 
Found in the Ferce ijlandi, Iceland, Bntanny, Hungary, Sile/it^ 
and Germany, generally accompanying other ll.ines of the 
genuS;, or in the (late of incruftation in contadl with Opal, 
Chalcedony, Prafe, Chryfoprafe, Serpentine, Granite, Ne' 
phrite, Jafper, Porphyry, and indurated Clay : colour white, 
yellow, red, or green : becomes gradually tranfparent when 
foaked in water by imbibing the liquid, and is (ometimes, 
though rarely, found in the form of a 3-fided pyramid: 
contains filica 93. alumina i or z. water, inflammaole mat- 
ter and air 5, with fometimes a little iron. 
'neeus. Qf ^ waxy luftre, and imperfe£lly conchoidal texture. 
Pitchftone. Kirnuan 1. p. 292. Schmeifser miner. 1. p. 145. 
Pitchftone. Thom/on chem. ‘i- p. ^Zi), 
Found in amorphous maifes of various (ize, in France, Germany> 
Saxony, and various parts of Europe, aiid in flenu Spain : co- 
lour grey i(h- black, greenidi-brown, blucifh grey, leek or 
olive-green, red or yellowilh, tranfparent, fetnitranfparent or 
opake, frequently prelenting large or fmall grained dillinft 
concretions: lullre a little greafy: fpecihc gravity from 
2,314. to 2,645. contains filica 73,co. alumina 14,50. lim« 
1,00. oxyde of iron 1 ,00. oxyde of manganefe 0,10. foda 
1,75. water 8,50, Klaproth, 
