- Varieties of Turquoise
- Formation & Sources of Turquoise
- Physical & Optical Properties of Turquoise
- Test and Identification of Turquoise
- Valuation and Buying Tips for Turquoise
- Synthetic Turquoise
The copper content of turquoise is responsible for its blue color,
and the presence of iron accounts for a common greenish cast. Since the
copper is an essential constituent and iron is also regarded as such
by many, turquoise is classed as an idiochromatic stone. The following
grading terms have been used in the trade to indicate the quality of
turquoise, but they do not necessarily denote geographical origin:
- Persian
This variety is intense medium blue and is the least porous of the turquoises; therefore, it has a slightly higher specific gravity than most material and takes a much better polish. - American or Mexican
Pale blue to light blue, as well as greenish blue to bluish green, characterize this type. In addition, it is often somewhat porous. - Egyptian
The variety of turquoise called Egyptian is greenish blue to yellowish green. Although it usually has a lower porosity and a higher density than American turquoise, the color is poorer, because of a higher iron content. - Turquoise Matrix
Specimens containing portions of the mother rock are called turquoise matrix. Stones with included matrix resembling a spider web pattern are the most important of this type.
