FLOOR.] 
MINERALS. 
189 
Hessiteand Petzite are the teilurides of Gold and Silver, Naumarmite Div. II. 
the corresponding selenide of Silver, while Argentite is the sulphide of Case 5 00 
Silver. The latter are cubic in crystallisation, but the silver sulphide is 
a dimorphous mineral presenting itself as Acanthite in forms belonging 
to the orthorhombic system. To this system belongs also Copper- 
glance, a valuable ore of Copper, the " cuprous" sulphide. Among the 
other important minerals in this section, a cubic series of mono- Case 7 (*• 
sulphides occurs which includes two commercially very important 
ores — Galena, the sulphide of lead, and Blende, the sulphide of zinc. Cases 5 (ii.) 
A Rhoinbohedral series includes Covelline, the cupric sulphide, and 6 * 
Cinnabar, or mercuric sulphide, the unique ore of the important metal Oases 7&8. 
Mercury. Millerite is the nickel monosulphide, and Greenockite, a 
rare mineral in bright yellow crystals, consists of the corresponding 
cadmium sulphide. 
There is also an important series of disulphides wherein Hauerite Case 8. 
and Iron-pyrites, which are respectively the persulphide of manga- 
nese and of iron, are cubic, while as Marcasite the latter com- 
pound is orthorhombic in crystallisation. These two forms of iron 
persulphide are frequent and familiar minerals. Iron-pyrites being 
conspicuous for its sharply defined forms, and Marcasite, or ** White 
Iron-pyrites," for the fantastic groupings in its crystallisation that 
have obtained for it the various names of Spear pyrites, Cocks- 
comb pyrites, &c. 
Molybdenite (Mo S 2 ) and Realgar (As 2 S 2 ) are severally molybdenum Case 9. 
and arsenic disulphides; the former a rhombohedral, the latter an 
oblique mineral. 
Here also is included Laurite, the rare ruthenium sulphide. 
Among the trisulphides we find some important compounds of the 
triad elements crystallising in the orthorhombic system. They are 
Orpiment, or arsenic trisulphide (As 2 S.J, and the two isomer- Case 9. 
phous trisulphides of Bismuth and Antimony, Bismuthite (Bi 2 S a ) 
and Antimonite (Sb 2 S. } ). Of both the last minerals, and in 
particular of Antimonite, very fine specimens are in this Table Case. 
Antimonite is an important source of the metal Antimony. 
Tho third section of the division is composed of minerals wherein cer- Sect. iii. 
tain arsenides, &c, of Section i. are combined with sulphides of Section 
ii., or which may be looked on as the result of a replacement of half 
the Arsenic of the minerals in the former section by its equivalent of 
Sulphur. Of these there is a cubic series, including Cobaltine, or Case 10. 
Cobalt-glance, the " Silver White Cobalt" of early mineralogists, a 
€obalt Sulphide with part of the Sulphur replaced by Arsenic and 
part of the Cobalt by Iron j (Co, Fe) (S. As) 2 1 . In Gersdorfite or 
Arsenical Nickel-glance, half the Sulphur is replaced by Arsenic, and 
in Ullraannite or Antimonial Nickel-glance by Antimony and Arsenic. 
In this section, also, the minerals of this chemical type exhibit a 
dimorphism similar to that of Pyrites and Marcasite among the disul- 
phides of Section ii., and of Rmamelsbergite and Chloanthite among 
the diarsen^des of Section i.; for in Mispickel and Glaucodote we Case 10. 
