CLASSIFICATION. 91 
4. DESCRIPTIONS OF MINERALS. 
CLASSIFICATION, 
Some of the prominent points in the classification of minerals 
adopted in the following pages are given in connection with the 
remarks on chemical composition, pages 79. 
Many instructors in the science, and most of those who con- 
sult a work on Mineralogy for practical purposes, prefer an ar- 
rangement of the ores which groups them under the head of the 
metal prominent in their constitution. The method of group- 
ing mineral species according to the basic element has therefore 
been here, to a large extent, followed. An exception has been 
made in the case of the silicates, because it is witb them almost 
linpracticable, on account of the number of basic elements they 
often contain; and, moreover, not more than half a dozen use- 
ful ores exist among them. ‘The silicates therefore, which in- 
clude the larger part of all minerals, make together one of the 
grand divisions in the classification, and they are presented ac- 
cording to their natural groups, in the same order as in the 
larger mineralogy. . 
The prominent subdivisions in the classification are as fol- 
lows: 
I. Tue Acrpic DIvISION, including the acidic elements oc- 
curring native, and the native compounds of the acidic elements 
with one another. 
Il. THe Basic Division, including the basic elements occur- 
_¥ing native, and the native binary and ternary compounds of 
the basic elements—the silicates excepted. 
IIT. Sinica and the Sruicarzs. 
IV. THE Hyprocarson Compounns, including mineral oils, 
resins, wax, and coals. 
The following are the chief subdivisions under these heads: 
I. Acinic Division. 
1. Sulphur Group.—The chief oxide a trioxide, its formula 
RO,. Includes Sulphur and sulphur oxides; Tellurium and 
tellurium oxides ; Molybdenum sulphide and oxide ; Tungsten 
Oxide. 
