Natural Red Spinel: magnification

Natural blue Spinel: magnification, spectrum, polariscope reaction, fluoriscence,
color filter reaction (possibly)

All corundum: RI, SG, birefringence, optic character, magnification, fluorescence, spectrum Identifying Characteristics and information
Cross hatch effect in polariscope, gas bubbles, curved striae in red variety. Spectral Data
Typical of dopant used. Natural blue spinel has 4600 band due to iron(not currently seen in syn. spinel). Trade Names and Misnomers
Alumag
Aqua Gem (M)
Aquagem
Berylite
Brazilian emerald (M)(2)
Corundolite
Dirigem
Emerada
Hope sapphire (M) ]]> http://www.all-gemstones.com/spinel-synthetic/feed 0 http://www.all-gemstones.com/spinel http://www.all-gemstones.com/spinel#comments Tue, 11 Aug 2009 10:19:22 +0000 admin http://www.all-gemstones.com/?p=1317

Natural Spinel Gemstone

Refractive Index : 1.718 (+0.017 – 0.008)

Optical Characteristic : SR

Specific Gravity : 3.60 (+0.10 – 0.03)

Formula : MgAI2O4

Crystal System : Cubic

Variety/Species : Spinel

Species/Group : Spinel Group

Birefringence : none

Dispersion : 0.020

Hardness : 8

Toughness : good

Ultrasonic : Usually safe

Steam : usually safe

UV Long : Red, orange and pink : Inert to weak red to orange-red (SW); weak to Strong red and orange (LW)Cobalt blue (rare) : Strong chalky whitish green (SW); strong red (LW) Near colorless and light green (both rare) : Inert to moderate orange to orange-red (LW) All other colors : Virtually inert

UV Short : See above

Pleochroism : None

Strength : N/A

Pleochroism Colors : None

Heat : May change color

Acids : No reaction

Light : stable

Polish Luster : vitreous to subadamantine

Fracture : conchoidal

Fracture Luster : Vitreous

Clarity Type : ll

Tones : 2-8

Saturations : 1-5

Cause of Color : Blue – iron, cobalt (rare); Red/pink – chromium

Enhancements : none

Cleavage : None

Color Range : bluish violet, violetish blue, blue, greenish blue, red-purple, purple-red, violet, grayish blue red-orange, orange-red, red, purple, bluish purple, grayish green yellow, (rarely), brownish black, black, (Black:see ceylonite).

Transparency : Transparent to opaque

Phenomena : Color change Asterism (rare)

Separations : Natural Spinel from- Synthetic spinel : RI (except red and blue), magnification, fluorescence, (except red and pink) Synthetic blue spinel : Magnification, spectrum, polariscope reaction, fluorescence, color filter reaction (possibly) Synthetic red spinel : Magnification Pyrope garnet : RI, fluorescence All corundum : RI, SG, birefringence, magnification, pleochroism Kyanite : Optic character, magnification, spectrum Chrysoberyl : RI, birefringence, optic character, magnification, SG, spectrum Taaffeite : Optic character, birefringence Idocrase : Birefringence ( caution : Transparent idocrase may appear SR on refractometer and show strain in polariscope), optic character, spectrum, SG, color (possibly)

Identifying Characteristics and information Tiny octahedral crystals arranged singly or in “fingerprint” patterns. May have iron oxide staining. Part of a series that runs from gahnine, through gahnospinel to spinel. Spinel has more magnesium. When it has more zinc it is called Gahnite.

Spectral Data Red: 5400. Blue: 4330, 4580, 4600, 4780, 5080, 5550, 5850, 6350, 6750, 6850.

Trade Names and Misnomers Almandine Spinel(M) Balas ruby (M) Ceylonite(S) Chlorospinel Chrome Spinel Chromite(S) Chromohercynite Chrysoemelance Color change Spinel

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