FLOOR.] 
MINERALS. 
49 
Among the hydrated carbonates, and carbonates combined with Case 34 (ii. 
hydrates, or with compounds belonging to the previous divisions, 
attention may be called to the green and blue copper ores, Malachite 
and Chessylite, of which latter a very fine series of crystals is exhibited. 
Case 35 contains also fine specimens of Phosgenite, the combination Case 35 (i.) 
of the chloride and carbonate of lead and of Parisite, an analogous 
compound from the Emerald Mines of Santa Fe di Bogota, containing 
the fluoride combined with the carbonate of the rare metals of the 
Cerium group. 
The Silicates, occupying no less than fifteen Cases, form the next 
class in this section. The minerals comprised in this large, varied, 
and important class are arranged in series distinguished by the type of 
oxide that characterizes the bases in the silicate. Thus the silicates cor- 
responding to monoxide-bases (ferrous oxide, magnesia, &c.) are arrayed 
in one series; those the bases of which are epideutoxides (sesqui-oxides) 
are in another; and such as contain bases of both kinds fall into a third. 
The respective hydrates are comprised under the series to which the 
minerals of corresponding anhydrous types belong. 
The first of these series is composed of such silicates as are formed 
by silicic acid in association with monoxides only, or in which epideut- 
oxides (" sesqui-oxides") are met with only as accidental or intrusive 
ingredients. The anhydrous section of this series contains, among 
others, the following minerals. Phenakite, the di-glucinous silicate, and Case 36 (i.) 
Willemite, a corresponding and isomorphous silicate of Zinc, represent 
a rhombohedral series of dibasic silicates. The specimens of Phenakite 
from the emerald mines of the Urals are extremely fine. Of the same 
chemical type are the minerals comprised in the Olivine group, which 
are prismatic in their forms and include Tephroite, di-manganous 
silicate ; Fayalite, di-ferrous silicate ; with Olivine and Hyalosiderite, 
which are the magnesian and magnesio -ferrous silicates of the series. 
The Chrysolite is the name of the pale yellow gem into which tho 
larger and clearer specimens of Olivine are occasionally cut ; while tho 
Peridot is a pistachio-green variety, of which fine crystals and cut spe- 
cimens are exhibited in Case 36. Gadolinite is di-yttrious silicate 
(containing also cerium, &c.) ; and Humite, a mineral containing 
Fluorine, belongs also to the more basic silicates. 
Among the mono-silicates are arranged the large series of im- Cases 36 
portant minerals which form the two parallel groups of the Augites l u -) t0 3S. 
and the Hornblendes. In juxtaposition with these is seen Wollas- 
tonite, the calcic monosilicate, and the anorthic minerals Rhodonite Case 3S (ii.) 
and Babingtonite, homotypic in composition, but crystallographically 
differing from the other members of the series. The Augitic and 
Hornblendic groups present two distinct crystallographic types. In 
Enstatite, the magnesian silicate crystallizes in the prismatic system, Case36(ii.) 
though with certain of the angles of an Augite ; while in the obliquely- 
crystallizing Diopside, and the other Augites, part of the magnesium 
is displaced by Iron, Manganese, Calcium, or Zinc. So Anthophyllite, Case 38 (i.) 
a magnesio-ferrous monosilicate, presents prismatic forms with angles 
belonging to the type of the Hornblendes, as exemplified in Tremolitc 
and the other members of the group, which, however, crystallize in 
