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Attributes of Crystals @ Jewel Info 4 U
By:Ritika
The physical attributes of crystals
need to be studied in detail for the
categorization of crystals. This is
a highly specialized field of
crystallography.
There are various methods for
categorizing a crystal. Generally
the two common methods used for
crystal categorization are:
* On the basis of crystalline
structure
* On the basis of chemical or
physical attributes
There are some main differences
between facets and attributes of
crystals in crystallography. Facets
tell us about the actual
classification system, i.e. the
scheme and structure of crystals.
But attributes of crystals in
crystallography are simple values,
not associated with a classification
system. Also, attributes of crystals
differ and are intrinsic to the
nature of an object.
Crystal Groups Based on Lattices:
 On the basis of lattices or shape
attributes of crystals, the crystals
can be divided into seven crystal
lattice systems. They are:
* Cubic which is also termed as
Isometric: This include in it
crystals of eight faces also termed
octahedrons or crystals of 10 faces
also termed dodecahedrons. Also, it
is vital that cube faced crystals do
not belong to this type of crystal
lattice systems.
* Tetragonal: This has attributes
same as cubic crystal lattice system
with an additional attribute of
being one axis longer. These form
double pyramids and prisms shaped
crystals.
* Orthorhombic: This has attributes
similar to tetragonal crystals but
do not have a square shape in cross
section. These form rhombic prisms
or dipyramids shaped crystals.
* Hexagonal: These include six-sided
prisms with the cross section
focusing a hexagon.
* Trigonal: This has single 3-fold
axis of rotation.
* Triclinic: This crystal lattice
system generally does not have
normal shape. The reason for such
shapes in this crsytal lattice
system is because the crystal is not
symmetrical from one side to the
other.
* Monoclinic: One instance of the
monoclinic crystal lattice system is
skewed tetragonal crystals. These
include prisms and double pyramids
shaped crystals.
Crystal Groups Based on Physical
and Chemical attributes:
On the basis of physical and
chemical attributes, crystals can be
divided into four main categories.
They are:
* Covalent Crystals:
Covalent crystals possess true
covalent bonds with all atoms in the
crystal thus focusing it as a big
molecule. Another vital attribute
possessed by crystal belonging to
covalent crystals is that they have
high melting points. Some crystals
to name in the category of covalent
crystals are diamond and zinc
sulfide crystals.
* Metallic Crystals:
In the metallic crystals the outer
electrons move freely around the
lattice. This is because each metal
atoms present in the metallic
crystals lie on lattice sites.
Another vital attribute possessed by
crystal belonging to metallic
crystals are they have high melting
points and they are very dense.
* Ionic Crystals:
The ionic crystals possess ionic
bonds and are bound together by
electrostatic forces. One instance
to name in the crystal to name in
the category of ionic crystals is
table salt. The vital attributes of
ionic crystals are that they are
hard and have high melting points.
* Molecular Crystals:
Molecular crystals possess
non-covalent interactions also
termed hydrogen bonding or van der
Waals force. The main attribute of
crystals belonging to molecular
crystals are that they are soft and
have low melting points. Some
instances of molecular crystals
category are rock candy which is
nothing but the crystalline form of
table sugar.
Let us study one example of crystal
physical attribute of the diamond.
Diamonds are high-pressure
polymorphs of carbon and are meta
stable at room temperature. Diamond
focus lattice spacing of 1.54 and
have closely packed carbon atoms.
The hardness attribute of diamonds
vary with the direction in the
crystal, the hardest direction being
normal to the octahedral face.
Diamonds have a conchoidal fracture.
The diamond can be cleaved in any
plane as cleavage occurs readily
parallel to the octahedral faces,
giving four directions of possible
cleavage. Diamonds occur in various
colors like colorless (white) and
pale yellow (off color or capes).
However, colors of the diamond in
blue, brown, red, orange, green,
pink and deep-yellow are also found.
Pink diamonds are due to to traces
of manganese. Generally, the color
of diamonds is widely thought to be
due to lattice defects rather than
trace elements.
A crystal named blue lace agate ia
pale blue with white or darker
lines. The crystal amber is Opaque
or transparent resin with insects or
vegetation trapped inside at times.
The amber occurs in golden brown or
yellow color and green amber occurs
due to artificially coloring. An
instance of transparent, pointed
crystals is amethyst which occurs in
purple to lavender color. The
red-green colored bloodstone crystal
appears as green quartz flecked with
red or yellow jasper. The hematite
crystal occurs in two colors namely
silver, red and has vital properties
like grounding and protecting. It
appears as red or gray when
unpolished, and shiny when polished.
Jade crystals that are translucent
are termed jadeites and those that
are creamy are termed nephrites. The
colors in which jade crystals are
available are green, orange, brown,
blue, blue-green, cream, lavender,
red and white. One instance of
opaque and patterned crystal is
jasper which is available in red,
brown, yellow, green, blue and
purple colors. The labradorite
crystal which is available in colors
grayish to black with blue and
yellow is usually polished, dark
until it catches the light and then
turns iridescent blue or has gold
flashes. Tiger's Eye quartz crystal
contains brown iron which makes it
get the golden-yellow color.
Crystals with higher degrees of
symmetry tend to generate more form
faces. Faces of particular forms
commonly share unique physical or
chemical attributes.
The absolute structure is the
concept of relating some external
macroscopic physical attribute of
crystals. In fact, the powerful rays
of color attribute of crystals speak
about the frequency of the energy
that they emit. Crystals have
specific attributes attached to each
of them as described above them.
These special attributes of each
crystal helps for a variety of
specific usages of crystals and also
for creating a stylish piece of
jewelry using carefully chosen
crystals.
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