An overview on Sapphirine Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of Sapphirine gems.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Monoclinic or triclinc; crystals tabular; usually granular or as disseminated grains.|
|Colors||Pale blue, bluish gray, greenish gray, green; depth of blue color varies with Fe. Also, (rarely) purplish pink.|
|Cleavage||Lndistinct; fracture uneven to subconchoidal.|
|Stone Sizes||Facetable sapphirine is exceedingly rare, even though the material occurs in transparent grains. GIA noted a very unusual purplish-pink stone of 1.54 cts, oval, with included mica “book” (phlogopite), from Sri Lanka; R.l. =1.701—1.707; β= 1.705; birefringence = 0.006; S.G.: 3.51. The refractive indices of sapphirine are close to idocrase, but the former is biaxial. Other such gems exist but have been misidentified.|
Mg3,5Al9Si4,5O20 (+Fe). Complex substitution of Mg/Al/Si with charge balancing.
Two polytypes: Sapphirine-2M = (Mg,Al)8(Al,Si)6O20; monoclinic. Sapphirine-Te=(Mg,Al )8(Al,Si)6O20; triclinic.
|Pleochroism||Distinct: X = pinkish buff; yellowish; pale smoky brown; colorless: Y=sky blue: sapphire blue: greenish blue; Z=dark sky blue; sapphire blue.|
Optics: a =1.714-1.716; β= 1.719-1.721; γ= 1.720-1.723.
Occurrence: In mineral veins or cavities in eruptive igneous rocks.
Milford, Utah; Keweenaw Peninsula, Michigan; Lake Superior, Minnesota.
Canada; Scotland; England: Sweden; Czechoslovakia;
Japan; South Africa; Greenland; Madagascar: Italy: Sri Lanka.
Name: In allusion to the (sapphire blue) color.