December – TOPAZ
| CHEMICAL COMPOSITION | Al2(F, OH)2 SiO4 |
|---|---|
| CUBIC CRYSTAL SYSTEM | |
| REFRACTIVE INDEX | 1.619-1.627 (+.010, -.010) |
| HARDNESS | |
| SPECIFIC GRAVITY | 3.53(+.04,-.04) |
| DISPERSION | 014 |
| CLEAVAGE | perfect in one direction |
| GIA GRADING |
Additional Information
Topaz is derived from the Sanskrit word "tapas," meaning fire. This is because Blue Topaz was considered by ancient civilizations to have cooling properties. This gemstone was credited with many other healing powers. Blue Topaz is the hardest of the silicate minerals. While pure Topaz is colorless, minor changes of elements within the stone result in a variety of other colors, such as blue, pale green, red, yellow and pink. The blue hue is created when Topaz is heated. The three shades of Blue Topaz are Sky, Swiss and London Blue. The latter is the deepest blue and is often used as a less expensive substitute for Sapphire. Topaz is found primarily in Brazil, Nigeria, Sri Lanka, Mexico, Pakistan, China, and the United States. A gift of Blue Topaz is symbolic of love and fidelity.
Appearance:
Misnomers: Brazilian sapphire
Typical Size Range: 5 to 25 ct; faceted stones over 2000 ct have been cut for museums
Typical Cutting Styles: faceted
Cleaning Methods:
References
Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
GIA. (n.d.). GIA Grading and Reports. Retrieved July 29, 2011, from Gemological Institute of America:
http://gia4cs.gia.edu/cm/grading-reports.htm
ICGA. (n.d.). All About Gems. Retrieved July 30, 2011, from International Colored Gemstone Association:
http://www.gemstone.org/index.php?option=com_content&view=section&layout=blog&id=1&Itemid=69
IGS. (n.d.). IGS Reference Library. Retrieved July 29, 2011, from Internatonal Gem Society:
http://www.gemsociety.org/info/info.htm
Appearance:
- Light blue to dark blue
- Transparent
- Phenomena: Chatoyancy (rare)
Misnomers: Brazilian sapphire
Typical Size Range: 5 to 25 ct; faceted stones over 2000 ct have been cut for museums
Typical Cutting Styles: faceted
Cleaning Methods:
- Ultrasonic: usually safe
- Steamer: risky
- Warm soapy water: safe
References
Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
GIA. (n.d.). GIA Grading and Reports. Retrieved July 29, 2011, from Gemological Institute of America:
http://gia4cs.gia.edu/cm/grading-reports.htm
ICGA. (n.d.). All About Gems. Retrieved July 30, 2011, from International Colored Gemstone Association:
http://www.gemstone.org/index.php?option=com_content&view=section&layout=blog&id=1&Itemid=69
IGS. (n.d.). IGS Reference Library. Retrieved July 29, 2011, from Internatonal Gem Society:
http://www.gemsociety.org/info/info.htm
