Ruby

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

Optical Characteristic : DR, uniaxial negative

Specific Gravity : 4.00 (+0.10 – 0.05)

Formula : AI2O3

Crystal System : Trigonal

Variety/Species : Ruby

Species/Group : Corundum

Birefringence : 0.008 to 0.010

Dispersion : 0.018

Hardness : 9

Toughness : Excellent

Ultrasonic : Usually safe

Steam : Usually safe

UV : Burma Ruby : Strong red (LW), moderate red (SW)

Ceylon Ruby : Strong orange-red (LW), moderate orange-red (SW)

Thai Ruby : Wear red (LW), inert (SW)

UV Short : See above

Pleochroism : 2 colors

Strength : weak to strong

Pleochroism Colors : Strong: purplish red/ orangy red.

Heat : Stable

Acids : Slightiy attacked by acids

Light : Stable

Polish Luster : Vitreous to subadamantine

Fracture : Conchoidal, to uneven

Fracture Luster : Vitreous

Clarity Type : ll

Tones : 5-8

Saturations : 4-6

Cause of Color : Chromium; possibly modified by iron and titanium

Enhancements :Method : Heating followed by controlled cooling
Effect : Reduces rutile-clouding by driving the rutile back into solid solution with the corundum

Prevalence : Occasional to common

Detection : Often undetectable, magnification (possibly)
Stability : Stable unless heated above 1600°C and then slowly cooled .

Special Care Instructions: none

Method: heating and slow cooling
Effect: improves or creates asterism in certain kinds of material.

Prevalence: occasional
Detection: often undetectable
Stability: stable unless heated above 1600° C and cooled.

Special Care Instructions: none

Method: diffusion (heating above 1900° C in the presence of titanium oxide or other coloring agents)
Effect: improves or creates asterism, or diffuses color onto the surface of the stone

Prevalence: occasional
Detection: immersion and magnification

Stability: stable
Special Care Instructions: treatment is shallow, so avoid recutting

Method: heating
Effect: removes purple or brownish color component

Prevalence: common
Detection: magnification (possibly)

Stability: stable
Special Care Instructions: none

Method: oil and dye
Effect: hides cracks and improves color

Prevalence: occasional
Detection: magnification
Stability: oil may dry, leak out, or change color
Special Care Instructions: clean carefully, avoid solvents

Method: glass filling in cavities and cracks
Effect: hides cracks and cavities; also adds weight

Prevalence: occasional
Detection: magnification, immersion
Stability: knocks and bumps can destroy filling
Special Care Instructions: extra care in handling and wearing

Cleavage : None. Frequant parting.

Color Range : Orangy red, red, through strongly Purplish red

Transparency : Transparent to opaque

Phenomena : Chatoyancy (very rare), asterism

Separations : Natural Ruby from-

Synthetic ruby : magnification, fluorescence (possibly)

Reddish garnets : RI (possibly), birefringence, optic character, pleochroism, spectrum, magnification

All spinel : RI, birefringence, optic character, pleochroism, magnification

Doublets : Magnificatioin, red ring, immersion, spectrum (possibly)

Chrysoberyl : RI, optic character, SG, spectrum

Sapphire and synthetic ruby doublet – Magnification, immersion, fluorescence, spectrum (possibly)

Natural ruby doublet – Magnification

Garnet and glass doublet – Appearance, magnification, RI (possibly), birefringence, optic character, pleochroism

Identifying Characteristics and information
Silk (fine needle-like rutile crystals)3 sets of rutile needles intersecting at 60 degree angles, fingerprint inclusions, hexagonal growth lines and color zoning .Never cleaven oiled stones with ultrasonic or steamer. Curved striae or curved growth lines indicate synthetic corundum.

Spectral Data
Strong doublet @ 6942/6928. Weaker lines @ 6680 and 6592. Also lines @ 4765, 4750 and 4685.