FLOOR.] 
MINERALS. 
43 
sulphide, Cinnabar, or mercuric sulphide, the unique source of the Case 7. 
important metal Mercury. Millerite, the nickelous rnonosulphide, 
and Greenockite, a rare mineral in fine little yellow crystals, consists 
of the corresponding sulphide of Cadmium. 
There is also an important series of disulphides wherein Hauerite Case 8. 
and Iron-pyrites, formed severally of the manganic and the ferric 
di-sulphide, are cubic, while as Marcasite the latter compound is pris- 
matic in crystallization. These two forms of the ferric disulphide 
are frequent and familiar minerals, Iron-pyrites being conspicuous for 
its sharply defined forms, and Marcasite, or "White Iron-pyrites," for 
fantastic groupings in its crystallization that have obtained for it the 
various names of Spear pyrites, Cockscomb pyrites, &c. 
Molybdenite (Mo S 2 ) and Realgar (As 2 S 2 ) are severally molybdous Case 9. 
and arsenic disulphides ; the former a rhombohedral, the latter an 
oblique mineral. 
Among the trisulphides we find some important compounds of the 
triad elements crystallizing in the prismatic system. They are Orpi- Case 9. 
ment, or arsenic trisulphide (As 2 S 3 ), and the two isomorphous trisul- 
phides of Bismuth and Antimony, Bismuthite (Bi 2 S.J 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 impor- 
tant source of the metal Antimony. 
The third section of the division is composed of minerals wherein cer- Section 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 displacement 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, an 
arseno-sulphide of Cobalt, Co As S; or Co As 2 ; Co S 2 . In Gersdorf- 
fite, or Nickel-glance, and Ullmannite or Antimonial Nickel-glance, 
half the sulphur in a nickelous disulphide is displaced by Arsenic and 
by Antimony respectively. 
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 Chloauthite among 
the diarsenides of Section i. ; for in Mispickel and Glaucodote we Case 10. 
find arseno-sulphides of Cobalt and Iron of the same chemical type 
as Cobalt-glance, but crystallized in the prismatic system. Thus the 
three homotypic series of cubic diarsenides, disulphides, and diarseno- 
sulphicles belonging to the three sections of this division might be 
treated as a single group, while the three corresponding trimetric 
series may be looked on as another such group. 
Besides the three sections already described, this division contains Section iv. 
a fourth, wherein metallic sulphides are so combined with sulphides 
of Arsenic, Tin, Iron, &c, as to produce a series of sulphur salts; Cases 10, 
in the constitution of which Sulphur plays the part which Oxygen ^> --• 
plays in the ordinary oxygen-salts. This section is a numerous one 
in point of species, and the following are a few minerals included in 
it that are especially worthy of note. 
