QUARTZ ROCK. SECONDARY ROCKS. 231 
In veins of this rock are found, in different countries, 
many kinds of metallic ores : among others, silver, iron, 
tin, copper, and lead. 
263. QU4RTZ ROCK is a simple mountain rocky usually 
of granular texture, and whitish colour. 
It sometimes contains mica, in which case it has a slaty 
form. 
In certain mountains of Scotland, and the Scottish 
islands, quartz rock is very abundant. On the Conti- 
nent it appears in Saxony, Bohemia, Silesia, and 
several other countries. We are informed that a 
mountain, 350 feet high, and near 5000 feet broad and 
long, one of the Altaisch chain, in Siberia, consists 
entirely of a milk-white quartz. 
The uses of quartz have been already described 
(76, &c.) This kind of rock does not contain metallic 
ores of any description. 
II. SECONDARY ROCKS. 
264-. SECONDARY ROCKS are composed of, or at least 
contain ivithin them, the mineralized remains of organic 
substances. These must necessarily have been formed 
at a period subsequent to the formation of those organ- 
ized bodies the remains of which they enclose; and they 
have apparently been formed by the deposition of water. 
Hence it is that, to distinguish them from rocks of the 
preceding class, they have received the appellation of 
secondary. They always rest upon or cover primitive 
mountains, and sometimes lean upon their sides or in- 
vest them. 
Werner, the celebrated German mineralogist, makes 
two divisions of secondary rocks. The first of these he 
denominates transition rocks, and states that they are 
less perfectly crystallized than the primitive rocks; 
and that they enclose the remains of marine animals, no 
species of which are at this time known to exist : the 
other division he terms jloetz, or flat rocks, because they 
