Mineral or Rock???
A mineral can be defined as a naturally occurring inorganic solid that possesses an orderly
internal structure and a definite chemical composition. Some people, like physicists, might
be guilty of picking up a rock and calling it a mineral. The term "rock" is less specific,
referring to any solid mass of mineral or mineral-like material. Common rocks are often
made up of crystals of several kinds of minerals. Lutgens and Tarbuck give the following list
of essential characteristics of a "mineral":
1. It must occur naturally.
2. It must be inorganic
3. It must be a solid
4. It must possess an orderly internal structure, that is, its atoms
must be arranged in a definite pattern.
5. It must have a definite chemical composition that may vary within
specified limits."
Emerald is the mineral beryl with
substitution defects of Cr(3+) or
V(3+) replacing Al(3+).
Beryl has the chemical composition
Be3Al2(SiO3)6 and is classified as a
cyclosilicate. It is the principal ore for
the element beryllium.
Tsavorite is a variety of the mineral garnet a
calcium-aluminosilicate with the formula
Ca3Al2Si3O12. Crystal form is cubic. Trace amounts
of vanadium or chromium provide the green color.
It is often called the Rolls-Royce of greens at
Cadillac prices. From a collectors perspective,
tsavorite is 200 times more rare than emerald, it is
cleaner, more brilliant and not oiled or treated in
any way.
Tourmaline is a large group of
aluminosilicate minerals, with
variable composition:
(Ca,K,Na)(Al,Fe,Li,Mg,Mn)3(Al,Cr,Fe,V)
6(BO3)3(Si,Al,B)6O18(OH,F)4
Elbaite is one of the forms found
as pink and green colors,
having the general formula
Na(Li,Al)3Al6(BO3)3Si6O18(OH)4. It
is a silicate with lithium content, a
relatively rare element. Crystal
forms are trigonal.
“Tourmaline: Nature's source of Negative Ions”
Is that why it’s in my hairbrush???
Tourmaline is one of the naturally pyroelectric
minerals. Pyroelectronic charge in minerals
develops on the opposite faces of asymmetric
crystals.
Peridot is the gem-quality form of the mineral
Olivine. It has the chemical composition
(Mg,Fe)2SiO4, with Mg in greater quantities than Fe.
The depth of green depends on how much iron is
contained in the crystal structure, and varies from
yellow-green to olive to brownish green. Peridot is
also often referred to as "poor man's emerald".
Olivine is a very abundant mineral, but gem-quality
peridot is rather rare. Peridot crystals have been
collected from some Pallasite meteorites
Polarized micrograph
Fe (2+)
in Td (SiO4)
sites
Quartz - SiO2 -simplest silicate
mineral, piezoelectric, chiral!
+ Ti(3+)
heat
Replace:
-S with I
-Zn with Hg
(at vertices)
-Zn with Ag
(in middle)
Replace:
-S with I
-Zn with Hg
(at vertices)
-Zn with Cu
(in middle)