(turʹquoise).

A semiprecious, opaque, porous gemstone, ranging in color from pale sky blue to dull green. It is composed of hydrous phosphate of aluminum with traces of copper (the blue color source) and iron (the green color source). When the blue stones are heated or exposed to the weather, they turn green, which sometimes happens when the stones lose their natural moisture with the passing of time. This may account for the seeming popularity of green turquoise stones in ancient times. The early Egyptians used turquoise for jewelry, and it is found on the Sinai Peninsula as nodules in a red sandstone.

Turquoise is easy to engrave because it is a comparatively soft stone. The high priest Aaron wore an engraved turquoise stone on his “breastpiece of judgment.” Inscribed upon it was the name of one of Israel’s 12 tribes, and it was positioned first in the second row of stones on the breastpiece. (Ex 28:2, 15, 18, 21; 39:11) The figurative “covering” worn by the king of Tyre is depicted as being adorned with turquoise along with every other sort of precious stone. (Eze 28:12, 13) Edom was Tyre’s “merchant” for turquoise, for which Tyre was willing to give some of its stores in exchange.​—Eze 27:2, 16.