EARTHS. ARGILLACEOUS. 39- Opalus. 133 
y‘Uor, 
Nearly opakc, breaking longinulinally into fibrous frac- 
tures, fpontaiieonfiy falling into crultole frag- 
ments. 
Ligniforra Opal. Kir’wati niimr,':! l.p, 295. 
Wood Opal. Schnwjjcr twner. i. p. 145. 
Wood Opal, Thcmf ncbem.-i-p.^^i^- 
Found in Hungary, in latgc nwffes which have the form of 
wood, ot a milk rcddifti or yellowifh-whitc, _ brown, or 
hvacinth colour: has a Ihining lurface, and i? generally 
femit.anfparci.t on the edges: fratfure when broken tianl- 
vtrfely conclioidal, when broken longitudinally exhibiting 
the texture of wood: is very brittle, and confidcred as 
fragments of wood impregnated with fcmiopal. 
Scmitranfparent, light, yellow, of a perfeftly conchoidal 
texture, 
Werner C>onH, mineral. 55 /). 121. , , - J 
Found in Poland and Hungary, in rounded fragments, and 
often imbedded in jafper and indurated clay : its colour is 
fometimes a waxen, foir.etimcs a honey-ycilow, Irequently 
verging to brown; itisbiittle, fliining very much inter- 
nally, and breaks into acute and often nearly difeoid frag- 
ments. 
Hard, lightifli, eafily braking into acute fragments. 
Semi Opal. Kirnnan mineral. 1. p- 290, 
Halb Opal. Schmejier mineral. 1.^. 144. 
Semi opal, Menilites. Phomfon chem. 'i- p 5 ^ 3 * 
Found in Poland, Bohemia, Hungary, .^liria, Saxony and Ger- 
many: colour various lliades of white, grey, yellow, red, 
brtrwn, often mixed together : diaphanous, or opakc, rarely 
tranfpaient : texture •more or lefs perfedfly conchaceous, and 
its luilre more or Itfs glalfy ; is very brittle, and loiuetimcs 
adheres to the tongue : fpecific gravity 2,540. contains fi- 
lica 85,5. oxyde of iron 0,5. water 11,0. alumina 1,0. lime 
0,3. Klaproth. 
Rcfledting a different colour according to its pofition as to, 
light, hardilh, lighiilh, diaphanous, breaking into 
rather obtufe fragments. 
Silex v gus. Piyit. r.ut xii. 3’ p- 68. ». 6. a. 
Achates fere pellucida, W ail/fft. l. p- 2tio.. ». 19. 
Vulgar Opal. Kirovan mine til . l./>. 289. 
Common Opal. Schmriper nihcr- 1 . /• ' 4 ' • 
Common Opal. ‘Ihoiijin chem, •^.p.^22. 
Found in Poland, Silcfia, Saxony, Hungary, and Germany, 
imbedded in other ftones, of a common form, rarely kidney- 
form or bolryoidal, Ihining a little internally, geneiallv lub- 
opake: colour white, yellow, red, green of various mmuiesr 
