Crystals are one of the
most common forms found in the mineral world. Any solid form
of matter, be they ions, molecules or atoms which become uniformly
organized into a regularly repeating pattern in three dimensions,
can be categorized as a crystal. So, everything from salt and
sugar cubes, to even ice, constitutes a form of crystal. Metals,
in general, also conform to a crystalline structure.
For the individual who
is drawn to the world of natural history, mineralogy and gemology,
however, this term takes on a very special and somewhat different
meaning. Everything from quartz and ruby, to garnet and diamond,
is the realm which fascinates lovers of crystals.
Classically, when one thinks
of crystals, the quartz family often comes to mind first. The
basic chemical composition of quartz consists of tetrahedra of
silicon dioxide (SiO2). In its purest form, quartz is completely
transparent (save for fractures and terminations). Quartz crystals
are prized for fine termination, clarity and symmetry. Geodes
are one fine example of quartz crystals grown undisturbed over
millions of years within isolated pockets.
Beyond the colorless form
of quartz are the colored variations, such as amethyst, citrine,
carnelian, rose quartz and smoky quartz. These are formed when
various stray elements are introduced when the crystals are slowly
forming. Chalcedony, jasper and onyx are fine examples of this
mineral when it is in a microcrystalline matrix infused with
Another family of crystals
which has captured the imagination of humans for eons is beryl.
Considered to be of precious quality, this mineral
Be3Al2(SiO3)6, is a form of beryllium aluminium cyclosilicate
and is often found in crystalline form.
Corundum is another family
of crystals which is formed from aluminum oxide (Al2O3). The
two most famous forms of this crystal are the ruby and the sapphire.
The queen of all crystals
must be given, however, to the diamond. Although it is no different
in composition to common carbon graphite, given enough heat and
pressure, either naturally or artificially, the octahedral form
of diamond can be created.
It is fascinating to note
that natural diamonds are only the third hardest substance! Aggregated
diamond nanorods and ultrahard fullerites are beyond a 10 on
the Mohs hardness scale!