6ARTHS. PONDEROUS. 7. GrofTopetra. 73 



1. Of a coaimon amorphous figure. 



2. Cryftallized in numerous forms and variations, the moft ufuat 



of which are the quadrangular and hexangular prifms, the 

 double quadrangular pyramid, the quadrangular table be- 

 villed at the edges, the S-fided plate, and the imall rhomb 

 with obtufe angles ot 105''. 



Cryftallized falphate of Baryte^. So-xverby Br, min. /, 70-1-2. 



Baroflenite. K-r-ixan inineral, !,/»> 136. 



Sulphat of Barytes. Thomfons chem, "^ p. 621, 



Common ponderous Spar, or Cawk. Schme://, min, l. p, 257. 



Found in various parts of Britain and Euro e^ and is the moft 

 common matrix of metallic ores : it is lometinicrs found in 

 powder, ofien jn amorphous maffes, often cryltallized : it is 

 fomctimes highly polifhed, generally diaphanous, and in its 

 cryftallized ilaie tranfparcnt and rt'fledlive : colour fnov^y, 

 filvery or blueifh, greyifh, greenifh, reddifh or yellowifh- 

 white, often flefh -colour, fmoke -colour, houey-co'our, vini- 

 ceous, rarely olive-green, or gree ilh or yellowifti-grey, or 

 greyifli-black, very rarely blue : the layers are generally 

 Itraight, fometimes incurved: the primitive form of its cryf. 

 tals, according 10 Hauy, is a rectangular prifm, whofe bafes 

 are rhombs, with angles of rof deg. 30. and 78 deg, 30. 

 fpecihc gravity 4430. contains by analyfis, pure barytes 

 67,2. fuiphuric acid 32,8, Withering, 



itfUatttia*. Of a rounded form, or coating other bodies.' 



Found on Mount Iherg in Hercyniat of a ftala(5titical origin and' 

 form, in other rtfpedls agreeing with Barytes vulgaris. 



"J. C'rOSSOPETR^Vv Confining of ponderous 

 earth, a larger portion of filica, and a fmaller 

 of alu^jna: lightifh, hard, parafitic, meagre, 

 cryftalline: not totally fohible in fuiphuric acid, 

 even in a boiling heat, melting with difficulty irs 

 t\\Q fire, 



hetcynica. Jq 4;, fided redanguTur tables or prifm's, tranfverfely flriate, 

 termirrating at one end in a needle point ^ two of them 

 cutting each other crofswife and longitudinally. 



Heyer chem. arinaU 1789. I./. 212. 



F^u.'id upon calcareous fpar, in the mines of Hercvnia, near 

 Andrecijbiirg^ in fmaller aggregate cryltals, fomctimes very 

 minute, rarely pellucid, oftener diaphanous or opake : co- 

 lour milk-white, hyaline, yeiloAilh, rot always itriking lire 

 with ilecl, yet frequently making a mark upon glafs : melts 

 with borax and foda, with ebullition. 



VOL Vil. — K 



