PYERHOSIDERITE. 



■zv^^os, yellow, and (rioy,^og, iron. See Pykosi- 



DEKITE. 



Pyrrhotinjs, Breithaupt. Hexagonal. 

 Earely crystallized, in irregular six-sided 

 prisms, variously modified. Perfect basal 

 cleavage. Generally occurs massive and 

 amorphous. Structure granular. Colour 

 bronze-yellow, reddish, or brownish : liable 

 to speedy tarnish on exposure to the air, 

 Opaque." Lustre metallic. Streak greyish- 

 black. Brittle. Fracture uneven, passing into 

 small imperfect-conchoidal. Acts slightly on 

 the magnet. H. o-5 to 4-5. S.G. 4*4 to 4-7. 



Camp. Sulohide of iron, or Fe^ S8 = iron 

 60-5, sulphur 39-5 = 100. 



Analysis, from Bodenmais, by H. Rose : 

 Iron ..... 60-95 

 Sulphur .... 39-05 



100-00 



BB on charcoal, fuses, forming a greyish- 

 black magnetic globule. Roasted in the 

 state of tine powder, it is converted into 

 pure peroxide of iron. 



Soluble in muriatic acid, leaving a residue 

 of sulphur^ 



Localities. — English. Cornwall: Botal- 

 lack, near St. Just ; Huel Maudlin (cleav- 

 able). Beeralston, Devonshire. Several 

 mines near Aldstone, Cumberland. — Welsh. 

 Isear the base of Moel Elion, and Llanrwst, 

 Caernarvonshire. With Copper Pyrites, 

 Clogau Mine, near Dolgelly, Merionethshire. 

 — Scotch. Appin, Argyleshire, massive. 

 Xear Inverary. Galloway Hills. — Irish. 

 ]Sear Leahtown, Donegal, of a bronze colour. 

 — Foreign. Kongsberg, Norway; and An - 

 dreasberg, in the Harz, in crystalline plates. 

 Bodenmais, in Bavaria (cleavable). Kupfer- 

 berg, in Bohemia. Bernkastel, on the Mo- 

 selle. Saxony. Silesia. Salzburg. Siberia. 

 St. Jerome, Canada, in large veins. United 

 States. Minas Geraes, Brazil, in very large 

 crystals, 



Name. From ^ti^^orhs, reddish, in allusion 

 to its colour. 



Brit. Mus., Case 14. 



3I.F.G. Principal Floor, Wall-case 19 

 (Foreign). 



Pyrrhotine may be distinguished from 

 common Iron Pyrites by inferior hardness. 



Q. 



Quartz, Haiiy. See Rock Crystal. 

 Quartz, Kirwan. Common Quartz. 

 Quartz. Hexagonal. Occurs in hexa- 

 gonal prisms, sometimes terminated at both 



QUARTZ. 311 



ends by six-sided pyramids. (See Rock 

 Crystal.) Colourless, when pure ; various 

 shades of yellow, red, brown, green, blue, 

 \ iolet and black. Transparent to opaque. 

 Lustre vitreous, sometimes inclining to 

 resinous. Streak white; of impure varie- 

 ties the same as the colour, but paler. 

 Tough, brittle, or friable. Uncleavable, 

 Fracture conchoidal. H. 7. S.G. 2*5 to 2 8. 



Fig. 355. 



Comp. Si ; pure silica in the insoluble 

 state, or that cannot be taken up by a 

 potash solution. 



BB alone, undergoes no change; with 

 soda fuses readily with efflorescence to a 

 transparent glass'. 



Insoluble in all acids except hydrofluoric 

 acid. 



Name. Probably a German word, signi- 

 fying the grating "sound made by clay in 

 kneading it. 



The Quartz family is divided into three 

 groups, viz . : 



I. The UeVreoMs, comprising those varieties 

 which present the bright, glassy lustre of 

 broken Rock Crystal ; and including Ame- 

 thyst, Aventurine, False Topaz, Ferruginous 

 Quartz, Milky (and greasy) Quartz, Rock 

 Crystal, Rose Quartz, Slderite, Smoky 

 Quartz, or Cairngorum. 



II. The Chalcedonic, including those va- 

 rieties which display the glistening sub- 

 vitreous or Avaxy lustre, and the transiucency 

 or transparency of Chalcedony; as Agate, 

 Carnelian, CafsEye, Chalcedony, Chrysoprase, 

 Flint, Hornstone, Mocha Stone, Onyx, Sard, 

 Sardonyx, &iC. 



III. The Jaspery, or the varieties pre- 

 senting the dull colours, lustre, and opacity 

 of Jasper ; as Bloodstone or Heliotrope, Jasper, 

 Lydian Stone, Touchstone, or Basanite ; 

 also FihrGus Quartz, Floatstone, Granidar 

 Quartz, Haytorite, Phthanite {Kieselschiefer), 

 Sandstone, Siliceous Sinter, Silicijied Wood, 

 &c. 



Brit. Mus., Cases 21 and 22. 



M.F. G. In Hall — Auriferous Quartz from 

 the Grass Valley, Nevada county, California. 

 Mass of crystallized Quartz from a mine in 

 Weardale," Durham. Large crystal from 

 Brazil, under Case HI., in Entrance Hall. 



X4: 



