This
mineral is remarkable among all the gem minerals in not being
transparent and in never occurring in the form of a fine crystal. In
composition turquoise is a hydrus phosphate of aluminum. The gem is
rather soft; its grade is No. 6.
The
ancient supply of fine turquoise came from a mine not far from
Nishapur, in Persia, and the mining of the gems in that locality is
said to have supported the entire population of the town. The mines
must be very ancient. A description of one was written in the year 1300
a.d. and according to a
popular tradition, one of the mines, known as Isaac's Mine, was opened
by Isaac, son of Abraham. At the present time most of the turquoise
come from New Mexico. These mines also are very old and were first
worked by the Spaniards, it is said, by consent of the Indians, who
still inhabited the land.
The predominating color of the turquoise is green, while on the other hand the color of
