Archive for the Rare Gemstones Category

  • Star Diopside

    Refractive Index : 1.701 – 1.675 (+0.029 – 0.010)

    Optical Characteristic : DR, B+,  AGG

    Specific Gravity : 3.29 (+0.11 – 0.07)

    Formula : CaMgSi2O6

    Crystal System : Monoclinic

    Variety/Species : Diopside

    Species/Group : Pyroxene group

    Birefringence : 0.024 to 0.030

    Dispersion : N/A

    Hardness : 5.5 to 6

    Toughness : poor

    Ultrasonic : risky

    Steam : Never

    UV Long : weak

    UV Short : Inert

    Pleochroism : 2 or [...]

  • Star Beryl

    Refractive Index : 1.583 – 1.577 (+0.017 – 0.017)

    Optical Characteristic : DR, U-

    Specific Gravity : 2.72 (+0.18 – 0.05)

    Formula : Be3Al2Si6O18

    Crystal System : Hexagonal

    Variety/Species : Star Beryl

    Species/Group : Beryl

    Birefringence : 0.005 – 0.009

    Dispersion : 0.014

    Hardness : 7.5 to 8

    Toughness : good

    Ultrasonic : risky

    Steam : risky

    UV Long : Inert

    UV Short : Inert

    Pleochroism : 2 colors

    Strength : [...]

  • Sphalerite

    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 [...]

  • Spurrite

    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 : [...]

  • Staurolite

    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 [...]

  • Stibiotantalite

    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 [...]

  • Stichtite

    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 [...]

  • Taafeite

    Refractive Index : 1.723 – 1.719 (+0.002 – 0.002)

    Optical Characteristic : DR, U-

    Specific Gravity : 3.61 (+0.01 – 0.01)

    Formula : BeMg3AI8O16 + Fe, Mn, Zn, V, Cr.

    Crystal System : Hexagonal

    Variety/Species : All

    Species/Group : Taafeite

    Birefringence : 0.004 to 0.005

    Dispersion : 0.019

    Hardness : 8 to 8.5

    Toughness : good

    Ultrasonic : risky

    Steam : risky

    UV Long : Inert to weak

    UV [...]

  • Tantalite

    Refractive Index : 2.430 – 2.260

    Optical Characteristic : DR, B+

    Specific Gravity : 8.2 – 5.5

    Formula : MnTa2O6

    Crystal System : Orthorhombic

    Variety/Species : All

    Species/Group : Tantalite

    Birefringence : 0.160

    Dispersion : N/A

    Hardness : 6 to 6.5

    Toughness : poor

    Ultrasonic : Never

    Steam : Never

    UV Long : Inert

    UV Short : Inert

    Pleochroism : 3 colors

    Strength : weak to moderate

    Pleochroism Colors : Strong: Brown/red-brown.

    Heat [...]

  • Tephroite

    Refractive Index : 1.825 – 1.770

    Optical Characteristic : DR, B-, AGG

    Specific Gravity : 4.11

    Formula : Mn2SiO4

    Crystal System : Orthorhombic

    Variety/Species : All

    Species/Group : Tephroite

    Birefringence : 0.037 – 0.047

    Dispersion :

    Hardness : 6

    Toughness : poor

    Ultrasonic : Never

    Steam : Never

    UV Long : Inert

    UV Short : Inert

    Pleochroism : 3 colors

    Strength : weak to moderate

    Pleochroism Colors : Moderate: Greenish blue/ [...]