Fluorite

Fluorite

Chemical Formula:  CaF₂

Chemical Composition:  Calcium iron silicate

Crystal System:  Cubic (Isometeric)

Mineral Group:  Garnet

Varieties of Andradite:  Demantoid, Melanite, Topazolite

Hardness:  6 — 7

Density/Specific Gravity:  3.7 — 4.1

Refractive Index:  1.88 — 1.94

Double Refraction:  None

Absorption Spectra:  701, 693, 640, 622, 443

Colour:  Black, brown, yellow-brown, greenish yellow, lemon yellow

Pleochroism:  None

Transparency:  Transparent, translucent, opaque

Lustre:  Vitreous (glassy), adamantine (diamond like – non-metallic) 

Luminescence: None

Cleavage:  None

Fracture:  Conchoidal 

Healing Stone:  No

Assigned Planet:  No

Additional Zodiac Stone:  No

Gemstone of the Month:  No

Countries:  Deposits are widespread. China, France, Germany, Italy, Korea, Mexico, Norway, Romania, Russia, South Africa, Switzerland, the USA

Notes:  Demantoid is the most valuable garnet and has a diamond like lustre. Deposits found in China, Korea, Russia, USA, and Zaire.
Melanite deposts are found in France, Germany, Italy, and Colorado.
Topazolite looks like topaz and is yellow to lemon yellow in colour. Deposits found in California, the Italian Alps, and Switzerland.

andradite

Almandine

Chemical Formula:  Fe₃Al₂Si₃O₁₂

Chemical Composition: Aluminum, iron, silicon, oxygen

Crystal System:  Cubic (isometeric)

Mineral Group:  Garnet

Hardness:  7 — 7.5

Density/Specific Gravity:  3.93 — 4.30

Refractive Indicex:  1.770 — 1.820

Double Refraction:  None

Absorption Spectra:  617, 576, 526, 505, 476, 462, 438, 428, 404, 393

Colour:  Brownish red, red, blackish red, red with violet tint

Pleochroism:  None

Transparency:  Translucent, transparent

Lustre:  Vitreous (glass like appearance)

Luminescence: Inert

Cleavage:  None

Fracture:  Irregular/uneven

Healing Stone:  No

Assigned Planet:  Pluto

Additional Zodiac Stone:  Leo

Gemstone of the Month:  No

Countries:  Deposits found in Austria, Brazil, Czech Republic, India, Magagaskar, Sri Lanka, USA

Notes:  More Almandine gemstones are faceted than any other gemstone categorised in the garnet group.

 

almandine

Attribution: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons