http://www.all-gemstones.com www.all-gemstones.com    Mon, 15 Mar 2010 12:06:08 +0000 http://backend.userland.com/rss092 en 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 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 ... http://www.all-gemstones.com/tourmaline-group Refractive Index : 1.483 (+0.004 - 0.004) Optical Characteristic : SR, AGG Specific Gravity : 2.25 (+0.15 - 0.10) Formula : Na8AI6Si6O24CI2 Crystal System : Cubic Variety/Species : sodalite Species/Group : Sodalite group Birefringence : none Dispersion : none Hardness : 5 to 6 Toughness : poor Ultrasonic : Never Steam : risky UV Long : Inert to weak UV Short : Inert Pleochroism : ... http://www.all-gemstones.com/sodalite 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 ... http://www.all-gemstones.com/sphalerite 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 : ... http://www.all-gemstones.com/spodumene 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 ... http://www.all-gemstones.com/sphene 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 : ... http://www.all-gemstones.com/sogdianite 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 : ... http://www.all-gemstones.com/spurrite 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 ... http://www.all-gemstones.com/staurolite