Star Sapphire

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Refractive Index : 1.770 – 1.762 (+0.009 – 0.005)

Optical Characteristic : DR U-, AGG

Specific Gravity : 4.00 (+0.10 – 0.05)

Formula : AI2O3

Crystal System : Trigonal

Variety/Species : Sapphire

Species/Group : Corundum

Birefringence : 0.008 to 0.010

Dispersion : 0.018

Hardness : 9

Toughness : Good to excellent

Ultrasonic : Usually safe

Steam : usually safe

UV Long : Inert to strong

UV Short : Inert to strong

Pleochroism : 2 colors

Strength : weak

Pleochroism Colors : weak to none

Heat : stable

Acids : No reaction

Light : stable

Polish Luster : vitreous to subadamantine

Fracture : conchoidal

Fracture Luster : Vitreous

Clarity Type : ll

Tones : N/A

Saturations : N/A

Cause of Color : Iron , chromium, and titanium

Enhancements : Heating, diffusion, oil, dye

Cleavage : None.Frequant parting.

Color Range : Pink, purple, violet, green, blue, brownish yellow, grayish blue, reddish purple, bluish purple, bluish violet, violetish blue, greenish blue, green-blue, blue-green, bluish green, yellowish green, yellowish, pinkish, brownish, blackish, grayish Brown, black, gray, are considered black star sapphires.

Transparency : Semitransparent to opaque

Phenomena : Asterism, 6 ray star, 12 ray star Usually 6 ray.

Separations : Star Sapphire from-

Synthetic star sapphire : magnification, fluorescence (possibly)

Star spinel : RI, SG, optic character, magnification, spectrum

Star diopside : RI, SG, appearance

Identifying Characteristics and information
Silk (fine needle-like rutile crystals), 3 sets of rutile neddles intersecting at 60 degree angles, fingerprint inclusions, hexagonal growth lines, and color zoning.

Spectral Data
Lines at 4500, 4600, 4700.

Trade Names and Misnomers
Star Sapphire
Star topaz (M)

Tags: sapphire, star sapphire, Trigonal