http://www.all-gemstones.com www.all-gemstones.com    Thu, 06 May 2010 12:29:47 +0000 http://backend.userland.com/rss092 en 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 ... http://www.all-gemstones.com/smithsonite 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 ... http://www.all-gemstones.com/smoky-quartz Refractive Index : 1.490 (+0.020 - 0.010) Optical Characteristic : SR, ADR Specific Gravity : 2.40 (+0.10 - 0.07) Formula : Mostly silica. Crystal System : Non-crystalline Variety/Species : obsidian Species/Group : glass-natural Birefringence : none Dispersion : N/A Hardness : 5 to 5.5 Toughness : Fair to good Ultrasonic : Usually safe Steam : risky UV Long : Inert UV Short : Inert Pleochroism ... http://www.all-gemstones.com/snowflake-obsidian Refractive Index : 1.728 (+0.012 - 0.008) Optical Characteristic : SR, ADR Specific Gravity : 3.64 (+0.02 - 0.12) Formula : MgAI2O4 Crystal System : Cubic Variety/Species : All Species/Group : Synthetic spinel Birefringence : none Dispersion : .020 Hardness : 8 Toughness : good Ultrasonic : Usually safe Steam : usually safe UV Long : Inert to strong UV Short : Inert to ... http://www.all-gemstones.com/spinel-synthetic 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 ... http://www.all-gemstones.com/star-diopside 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 : ... http://www.all-gemstones.com/star-beryl Refractive Index : 1.673 - 1.663 (+0.010 - 0.010) Optical Characteristic : DR, B+ Specific Gravity : 3.25 (+0.15 - 0.02) Formula : MgSiO3 Crystal System : Orthorhombic Variety/Species : Enstatite Species/Group : Pyroxene group Birefringence : 0.008 to 0.011 Dispersion : none Hardness : 5 to 6 Toughness : poor Ultrasonic : risky Steam : Never UV Long : Inert UV Short : ... http://www.all-gemstones.com/star-enstatite 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 ... http://www.all-gemstones.com/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 : 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 ... http://www.all-gemstones.com/star-sapphire Refractive Index : 1.718 (+0.017 - 0.008) Optical Characteristic : SR Specific Gravity : 3.60 (+0.10 - 0.03) Formula : MgAI2O4 Crystal System : Cubic Variety/Species : spinel Species/Group : Spinel Group Birefringence : none Dispersion : 0.020 Hardness : 8 Toughness : good Ultrasonic : Usually safe Steam : usually safe UV Long : Inert to strong UV Short : Inert to weak Pleochroism ... http://www.all-gemstones.com/star-spinel