Archive for the Natural Gemstones Category
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Refractive Index : 2.50 – 2.369
Optical Characteristic : SR
Specific Gravity : 4.05 (+0.05 – 0.15)
Formula : ZnS + Fe
Crystal System : Cubic
Variety/Species : Sphalerite
Species/Group : sphalerite Group
Birefringence : none
Dispersion : 0.156
Hardness : 3.5 to 4
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert to strong
UV Short : Inert to strong
Pleochroism : None
Strength : N/A
Pleochroism [...]
-
Refractive Index : 1.676 – 1.662 (+0.005 – 0.005)
Optical Characteristic : DR, B+
Specific Gravity : 3.18 (+0.03 – 0.03)
Formula : LiAISi2O6
Crystal System : Monoclinic
Variety/Species : spodumene
Species/Group : Pyroxene group
Birefringence : 0.014
Dispersion : 0.017
Hardness : 6.5 to 7
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : 2 colors
Strength : moderate
Pleochroism Colors [...]
-
Refractive Index : 2.034 – 1.900 (+0.020 – 0.020)
Optical Characteristic : DR, B+
Specific Gravity : 3.52 (+0.02 – 0.02)
Formula : CaTiSiO5
Crystal System : Monoclinic
Variety/Species : All
Species/Group : sphene
Birefringence : 0.100 to 0.135
Dispersion : 0.051
Hardness : 5 to 5.5
Toughness : Fair to poor
Ultrasonic : risky
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : 3 colors
Strength [...]
-
Refractive Index : 1608 – 1.606
Optical Characteristic : DR, U-
Specific Gravity : 2.90 – 2.76
Formula : (K,Na)2Li,Fe,AI,Ti)2Zr2(Si2O5)6
Crystal System : Hexagonal
Variety/Species : sogdianite
Species/Group : Osumilite group
Birefringence : 0.002
Dispersion :
Hardness : 5 to 7
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert to weak
UV Short : Inert to weak
Pleochroism : None
Strength : N/A
Pleochroism Colors : [...]
-
Refractive Index : 1.679 – 1.640
Optical Characteristic : DR, B-
Specific Gravity : 3.00
Formula : Ca5(SiO4)2(CO3)
Crystal System : Monoclinic
Variety/Species : All
Species/Group : spurrite
Birefringence : 0.039
Dispersion :
Hardness : 5
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : None
Strength : N/A
Pleochroism Colors : None
Heat : sensitive
Acids : sensitive
Light : stable
Polish Luster : [...]
-
Refractive Index : 1.746 – 1.736 (+0.015 – 0.015)
Optical Characteristic : DR, B+, AGG
Specific Gravity : 3.71 (+0.08 -0.06)
Formula : (Fe++,Mg)2AI9(Si,AI)4O20(O,OH)4
Crystal System : Monoclinic
Variety/Species : All
Species/Group : staurolite
Birefringence : 0.009 to 0.015
Dispersion : 0.021
Hardness : 7 to 7.5
Toughness : fair
Ultrasonic : risky
Steam : risky
UV Long : Inert
UV Short : Inert
Pleochroism : 3 colors
Strength : moderate
Pleochroism [...]
-
Refractive Index : 2.460 – 2.370
Optical Characteristic : DR, B+
Specific Gravity : 7.46 – 7.34
Formula : SbTaO4
Crystal System : Orthorhombic
Variety/Species : All
Species/Group : stibiotantalite
Birefringence : 0.090
Dispersion : 0.146
Hardness : 5 to 5.5
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : None
Strength : N/A
Pleochroism Colors : None
Heat : sensitive
Acids : sensitive
Light [...]
-
Refractive Index : 1.545 – 1.518
Optical Characteristic : DR, U+
Specific Gravity : 2.22 – 2.16
Formula : Mg6Cr2(CO3)(OH)16.4(H2O)
Crystal System : Trigonal
Variety/Species : All
Species/Group : stichtite
Birefringence : 0.027
Dispersion :
Hardness : 1.5 to 2.5
Toughness : poor
Ultrasonic : Never
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : None
Strength : N/A
Pleochroism Colors : None
Heat : sensitive
Acids : sensitive
Light [...]
-
Refractive Index : 1.670 – 1.520
Optical Characteristic : DR, B-, AGG
Specific Gravity : 3.785 – 3.630
Formula : SrCO3
Crystal System : Orthorhombic
Variety/Species : strontianite
Species/Group : Aragonite Group
Birefringence : 0.150
Dispersion : 0.008 – 0.028
Hardness : 3.5
Toughness : Fair to poor
Ultrasonic : Never
Steam : Never
UV Long : Inert to moderate
UV Short : Inert to moderate
Pleochroism : None
Strength : [...]
-
Refractive Index : 2.409
Optical Characteristic : SR
Specific Gravity : 5.13 (+0.02 – 0.02)
Formula : SrTiO3
Crystal System : Cubic
Variety/Species : strontium titanate
Species/Group : Synthetic Tausonite
Birefringence : none
Dispersion : 0.190
Hardness : 5 to 6
Toughness : fair
Ultrasonic : Usually safe
Steam : risky
UV Long : Inert
UV Short : Inert
Pleochroism : None
Strength : N/A
Pleochroism Colors : None
Heat : sensitive
Acids : [...]