The Color we identify as 'Turquoise' today can be attributed to the stones Bluish-Green tones that have adorned many pieces of Jewelry, expanding the celebration of cultures throughout its history, tracing back to the 17th century.
Turquoise's mineral composition is aluminum phosphate & hydrated copper
CuA16(PO4)4 ·)OH)8·5H2O
The material has a hardness of 5-6 on the Mohs Scale and is most often seen in a polished, cabachon cut and is primarily opaque (If you were to put a light source up against it, no light would show through the stone)
The South-Western US hosts several mines that produce a variety of Turquoise displaying an array of matrix and veining with beautiful color & patterns. A sample of Carico Lake with its green tones, Morenci -a darker blue with the classic display of pyrite matrix, Bisbee-an aqua medium blue with brown matrix, Royston with a lighter hint of brown veining and from the Campitos mine in Mexico with its classic black veining matrix.
Another famous Turquoise mine in the US known for producing striking lighter blue - blue material and often free of veining or Matrix and is coined 'Sleeping Beauty', from the Sleeping Beauty Mine in Globe, Arizona.
The beauty in the use of American Turquoise has to be credited to the talented artisans of the Native American tribes. Known as the 'Sky stone', often worn in Ceremonial practice or as a protective piece for spiritual journeying, these often large & symbolic patterned designs set in Sterling Silver are a classic, wearable jewelry totem.
The needlepoint & petite needlepoint jewelry pieces are easily identifiable by the use of turquoise
meticulously shaped into slivers and/or small circular cabs, and set to create beautiful patterns.
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 ZUNI Needle Point Â
NAVAJO Cluster Pendant · Earrings & Cuff
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The Gem of the Ancients · The Gem of PERSIA
Often referred to as Sky Blue or Robins Egg color , the 'blues' of Persian Turquoise have adorned many significant historical pieces. The Turquoise specimens featured in the video (below) are from the Baghu Mine in the Damghan County, Province of Semnan, Iran, mined during the mid 1970's.
During part of his tenure exploring local mining areas in his home country of Iran, Mr.Kambiz Zarrabi, a geologist from UCLA, purchased much of the leftover production from the small operation in Baghu during 1976 and began importing some of this material to Los Angeles, CA. His son, Kamyar Zarrabi, a Master Goldsmith has continued the tradition of working through the parcel of rough. A handful of these pieces from the original lot have been carefully selected for color & clarity . As a collaboration , a small collection of pieces are being designed!
The photograph below shows the nodular formation of the material.
TURQUOISE · BAGHU MINE
The map below shows the Baghu Mine as well as the historical Neyshabur Mine.
The historical Neyshabur Mine is often the most well known mine for Sky Blue Turquoise, having had the majority of production. This turquoise was often shipped to the city of Mashhad for cutting into various cabochon forms, always leaving some of the rough matrix on the bottom of the finished pieces for identification and authenticity.
  The Marie-Louise Diadem Â
           A renowned piece of Fine Persian Turquoise & Diamonds on display at the Smithsonian Museum
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The Neyshabur mine also produced quantities of material called 'Shajari' - inclusions of black, dark and lighter brown or yellowish metal oxides, creating the appearance of dendritic vegetation.
Treatment
Turquoise from around the world comes in different grades and in its natural state, is a fairly porous Gem.
The majority of Turquoise, in order to improve its density to be used in Jewelry will undergo a process of stabilization, making it less absorbent of oils and solvents while also adding durability to the piece.
Classic Persian Sky Blue Turquoise cradled in warm 18K gold & Diamonds.