Some crystals look very similar despite a total vast difference in its chemical composition.
For
example, carnelian and agate looks similar yet each has a different chemical
composition. A colour heated amethyst still retains an amethyst characteristic
despite the colour changes to a yellow Citrine.
An visual
check on the physical appearance merely assists us to round down the
possibilities. There are many other factors which contribute to determine the
crystal type. Tests and complex lab experiments are done by mineralogist to
accurately determine the crystal type.
Raw
crystal formation would ease identification. Below is a list of common factors
used.
· Colour – Categorized as transparent, translucent or
opaque. Raw sight observation of the crystal colour is helpful to round down
the possibilities of the crystal type. Rarity and price may also provide clues.
· Streak – Streak refers to the true colour of the crystal
contents in powdered form. This colour identification is more accurate compared
to the above as it accurately show the contents and traces of mineral
composition of a crystal.
· Hardness on Mohs scale – This scale has a predetermined
set of minerals which was identified by Friedrich Mohs to measure the hardness
of minerals from 1 to 10. Diamond sits at 10 while talc being the softest
mineral sits at 1 on the scale.
· Cleavage – The presence, clarity and angles of cleavages
on the crystal surface determines which crystal system (e.g. trigonal, cubic)
it belongs to. The smoothness and fractures of the cleavage surface also plays
a role in determining the crystal identity (e.g. grainy, jagged)
· Crystalline system or structure – The crystal lattice is
categorized by the arrangement and ties of the chemical composition (i.e.
atoms, molecules, ions). Amorphous are minerals with no crystalline structure
· Amount of Transparency – This measures the degree of light
that can pass through the crystal.
· Tenacity – This measures the strength of ties between the
chemical bonds. It is usually measured by the ultimate breaking force.
· Magnetism – This measures the degree of force exerted by magnet
· Luster – This measures the degree of light reflected from
the surface of the crystal. Luster is commonly categorized as metallic, non
metallic, adamantine, vitreous, waxy, pearly, silky, greasy and so forth
· Odor – This test is usually conducted on the crystal when
it is rubbed, heated, moistened, or tested with a specific chemical
· Taste – This test can only be conducted if the crystal is
soluble.
· Gravity – This test is usually done by comparing the
weight ratio of the crystal with the weight of an equal amount of water.
