48 
NORTH GALLERY. 
[upper 
Ihv. II Hessite and Petzite are the teilurides of Gold and Silver, Naumannite 
Case 5 (i.) the corresponding selenide of Silver, while Argentite is the sulphide of 
Silver. The latter are cuhic 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 
•Case 7 (i.) other importaut minerals in this section, a cubic series of mono- 
sulphides occurs which includes two commercially very important 
dasesS (ii.) ores — Galena, the sulphide of lead, and Blende, the sulphide of zinc. 
4lud 6 " A Rhombohedral series includes Covelline, the cupric sulphide, 
Ca?es 7 & 8. Cinnabar, or mercuric sulphide, the unique ore of the important metal 
Mercury. Millerite is the nickel monosulphide, and Greenockite, a 
rare mineral in bright yellow crystals, consists of the corresponding 
cadmium sulphide. 
Case S. There is also an important series of disulphides wherein Hauerite 
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 denned 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. 
Case 9. Molybdenite (Mo S 2 ) and Realgar (As 2 S 2 ) are severally molybdenum 
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 
Case 9. Orpiment, or arsenic trisulphide (As 2 S 3 ), and the two isomor- 
phous trisulphides of Bismuth and Antimony, Bismuthite (Bi 2 S 3 ) 
: nd 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. 
Sect. iii. The third section of the division is composed of minerals wherein cer- 
tain arsenidas, &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 
Case 10. Sulphur. Of these there is a cubic series, including Cobaltine, or 
Cobalt-glance, the " Silver White Cobalt" of early mineralogists, a 
Cobalt Sulphide with part of the Sulphur replaced by Arsenic and 
part of the Cobalt by Iron j (Co, Fe) (S. As) 2 j . In Gersdorfite or 
Arsenical Nickel-glance, half the Sulphur is replaced by Arsenic, and 
in Ullmannite or Antimonial Nickel-glance by x^ntimony 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 Rammelsbergite and Chloanthite among 
< 10. the diarsenides of Section i. ; for in Mispickel and Glaucodote we 
