Civil Engineering Reference
In-Depth Information
6
Minerals
The majority of the planet on which we live consists of inorganic, mineral mate-
rials. Stone consists of minerals in the form of crystals, and in general it is esti-
mated that there is 4000 times as much solid rock on the earth as there is water
in all the oceans put together.
There are thousands of different minerals. They can be characterized by colour,
lustre, translucence, weight, hardness and their ability to split, and also by chem-
ical formulae, because all types of crystal have their own unique chemical struc-
ture. In normal rock species there are only a few hundred different minerals, and
in a simple species there are seldom more than four or five different minerals.
Granite is made up of the minerals quartz, felspar and mica, the latter contribut-
ing sparkle. In a few cases minerals can be found in a pure state.
The first use of minerals can be traced back to Africa in the production of
colour pigments. These were retrieved from the earth through a simple form of
mining.
In chemistry minerals are divided up according to their chemical composition.
The most important groups include pure elements: sulphides, oxides, carbonates
and silicates. The most widespread of these is the silicates, while oxides and sul-
phides are mostly used as ore for the extraction of metals. In order to simplify the
picture one can reduce minerals into two groups:
metals
and
non-metals
.
The occurrence of minerals is most often quite local. The purer the mineral
when extracted, the easier it is to use. However, most minerals are extracted from
conglomerate rocks or different types of loose materials.
Certain minerals have a tendency to occur together in the natural environ-
ment. When looking for a certain mineral, it is usually straightforward to work
out where to find it.
Metallic minerals
Some minerals have a chemical composition which makes it possible to extract
metals from them. These minerals are usually mixed with other minerals in the
