Turquoise is a mineral that is a hydrous phosphate of copper and aluminium, that creates blue and green colored specimens. A rare and valuable stone in finer grades and a prized gem and ornamental stone for thousands of years the world over.
Around the 16th century, from the French language, taken either from either the word 'turquois' for Turkish or 'pierre turquin' meaning a dark blue stone. Even the finest of turquoise is fracturable, with a maximum hardness of under 6. Color is as variable as the mineral's other properties, ranging from white howlite to a powder or sky blue, and from a blueish green to a yellow lime. The blue is attributed to idiochromatic copper while the green may be the result of iron impurities or dehydration. While quite fine material that rivals Iranian stones is sometimes found, most American turquoise is of a lower grade. Arizona is currently the most famous producer of turquoise, with the vivid Bisbee Blue and Sleeping Beauty being a good example of the Arizona material quality.