topaz

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Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

Species:  Topaz
Mohs Hardness:  8 out of 10
Color:  Nearly all colors
RI:  1.619 to 1.627 (+/-0.010)
Birefringence:  0.008 to 0.010
SR/DR/AGG:  DR
Clarity Type:  Type I
​Optic Character:  Biaxial positive (common point is 0.001 from the low RI)
Pleochroism:  Varies (see below)
Spectrum:  Varies (see below)
SG:  3.53 (+/-0.04)
Routine Treatments:  Irradiation followed by heating (blue topaz)

topaz facts

Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

Topaz occurs in nearly every color.

The most valued color is known as Imperial Topaz, and ranges from orangy red to red.
​
Some topaz crystals are so large that they are weighed in kilos, not carats.
 
Topaz can take such a high polish that it is slippery to the touch.
 ​
​Topaz is a November birthstone.
 
Blue topaz is the 4th wedding anniversary gemstone.

​Imperial topaz is the 23rd wedding anniversary gemstone.
​

Photo courtesy of Sotheby's

topaz varieties

blue topaz

Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

Blue topaz is the most popular of all topaz colors.
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Although usually undetectable, most blue topaz has undergone a routine irradiation and heating process to achieve its attractive blue coloration.

Swiss Blue Topaz is bright blue, light in tone.

London Blue Topaz is a darker blue, dark in tone.

red, pink, purple & imperial topaz

​RI
1.619 to 1.627 (+/-0.010).  Red, pink and purple stones typically 1.629 to 1.637

Color
Pale pink to strong red, purplish red and reddish purple.  Imperial topaz is fine medium orange-red.

Magnification
Two-phase and three-phase inclusions, and inclusions containing non-miscible (unmixed) liquids.  Surface treatment results in spotty color.  Chips on facet junctions might reveal colorless material underneath.

Spectrum
Not Diagnostic

Fluorescence
Variable

golden topaz & smoky topaz

Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

​RI
1.619 to 1.627 (+/-0.010).  Orange, yellow and brown stones typically 1.629 to 1.637

Color
Brown, yellowish brown, yellow to pinkish orange to orange.

Magnification
Two-phase and three-phase inclusions, liquid inclusions in planes.  Surface treatment results in spotty color.  Chips on facet junctions might reveal colorless material underneath.

Spectrum
Not Diagnostic

Fluorescence
Variable

colorless topaz

Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

RI
1.619 to 1.627 (+/-0.010).  colorless stones typically 1.609 to 1.617

Color
Colorless

Magnification
Two-phase and three-phase inclusions, liquid inclusions in planes.

Spectrum
Not Diagnostic

Fluorescence
​Inert to weak yellow or green under LW, generally weaker under SW.