Archive for the Trigonal Category

  • Smithsonite

    Refractive Index : 1.849 – 1.621

    Optical Characteristic : DR, U-, AGG

    Specific Gravity : 4.30 (+0.15)

    Formula : ZnCO3

    Crystal System : Trigonal

    Variety/Species : smithsonite

    Species/Group : calcite group

    Birefringence : 0.225 to 0.228

    Dispersion : N/A

    Hardness : 4 to 5

    Toughness : poor

    Ultrasonic : Never

    Steam : Never

    UV Long : Inert to strong

    UV Short : Inert to strong

    Pleochroism : None

    Strength : N/A

    Pleochroism [...]

  • Smoky Quartz

    Refractive Index : 1.553 – 1.544

    Optical Characteristic : DR, U+, AGG

    Specific Gravity : 2.651 (+0.04 – 0.01)

    Formula : SiO2

    Crystal System : Trigonal

    Variety/Species : smoky

    Species/Group : Quartz

    Birefringence : 0.009

    Dispersion : 0.013

    Hardness : 7

    Toughness : good

    Ultrasonic : Usually safe

    Steam : risky

    UV Long : Inert

    UV Short : Inert

    Pleochroism : 2 colors

    Strength : weak

    Pleochroism Colors : Dark stones, weak: [...]

  • Star Ruby

    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 : Ruby

    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 [...]

  • Star Sapphire

    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 [...]

  • Tourmaline Group

    Refractive Index : 1.644 – 1.624 + 0.134 – 0.021

    Optical Characteristic : DR U-

    Specific Gravity : 3.06 + 0.20 – 0.06

    Formula : Na(Li,AI)3AI6(BO3)3Si6018(OH)4

    Crystal System : Trigonal

    Variety/Species : All

    Species/Group : Tourmaline Group

    Birefringence : 0.018 to 0.040

    Dispersion : 0.017

    Hardness : 7 to 7.5

    Toughness : Fair

    Ultrasonic : Risky

    Steam : Risky

    UV Long : Inert to weak

    UV Short : Inert [...]

  • 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 [...]

  • Tiger’s Eye

    Refractive Index : 1.553-1.554

    Optical Characteristic : DR, AGG

    Specific Gravity : 2.651 +.06 -.01

    Formula : SiO2

    Crystal System : Trigonal

    Variety/Species : Tiger’s Eye

    Species/Group : Quartz

    Birefringence : 0.009

    Dispersion : N/A

    Hardness : 7

    Toughness : Good

    Ultrasonic : Uaually safe

    Steam : Risky

    UV Long : Inert

    UV Short : Inert

    Pleochroism : None

    Strength : N/A

    Pleochroism Colors : None

    Heat : Avoid aburt temperature change

    Acids : [...]

  • Turritella Agate

    Refractive Index : 1.54 – 1.53

    Optical Characteristic : AGG

    Specific Gravity : 2.60 + 0.30 – 0.05

    Formula : SiO2

    Crystal System : Trigonal

    Variety/Species : Chalcedony

    Species/Group : Cryptocrystaline Quartz

    Birefringence : 0.004

    Dispersion : None

    Hardness : 6.5 to 7

    Toughness : Good

    Ultrasonic : Uaually safe

    Steam : Usually safe

    UV Long : Inert to moderate

    UV Short : Inert to moderate

    Pleochroism : None

    Strength : [...]

  • Watermelon Tourmaline

    Refractive Index : 1.644 – 1.624 (+ 0.011 – 0.009)

    Optical Characteristic : DR, U-

    Specific Gravity : 3.06 + 0.20 – 0.06

    Formula : Na(Li,AI)3AI6(BO3)3Si6018(OH)4

    Crystal System : Trigonal

    Variety/Species : Elbaite

    Species/Group : Tourmaline Group

    Birefringence : 0.018 to 0.040

    Dispersion : 0.017

    Hardness : 7 to 7.5

    Toughness : Fair

    Ultrasonic : Risky

    Steam : Risky

    UV Long : Inert to weak

    UV Short : Inert [...]

  • Uvite

     

    Refractive Index : 1.660 – 1.612

    Optical Characteristic : DR, Uniaxial negative

    Specific Gravity : 3.06 (- 0.20 – 0.06)

    Formula : CaMg3(AI5Mg)BSi6O27(OH)3(OH,f)

    Crystal System : Trigonal

    Variety/Species : Tourmaline

    Species/Group : Tourmaline Group

    Birefringence : 0.017 to 0.021

    Dispersion : 0.017

    Hardness : 7 to 7.5

    Toughness : Fair

    Ultrasonic : Risky

    Steam : Risky

    UV Long : Inert to weak

    UV Short : Inert to weak

    Pleochroism : [...]