| We begin with an outline
of the very basics of the relevant geology.
Minerals are the ‘building blocks’ of
rocks, the equivalent of atoms in chemistry. Most rocks contain more
than one of the 20-30 common minerals which constitute the rocks of
our planet.
Rocks are classified into three broad categories according to
their origin, i.e. igneous, sedimentary or metamorphic. Igneous rocks such as granite and basalt form
from magmas, hot natural liquids produced by the melting of older
rocks at depth. By contrast sedimentary
rocks like sandstone and limestone are the result of
weathering processes at the Earth’s surface: the weathering
products, e.g. quartz grains, are transported by water, wind or ice.
They are then deposited usually in horizontal layers which may
contain fossils. Metamorphic rocks like marble originate
by the heating (but not melting) of older rocks, a good analogy
being the firing of clay in a kiln to make pottery.
Significantly, igneous, sedimentary and metamorphic rocks outcrop
in this area of NE Ireland, displaying not only most of the common
minerals but also some exciting rarer ones.
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