The pastel shades of turquoise have endeared it to many great cultures of antiquity: it has adorned the rulers of Ancient Egypt, the Aztecs, Persia, Mesopotamia, the Indus Valley, and in ancient China since at least The Shang Dynasty.
Hardness and richness of colour are two of the major factors in determining the value of turquoise; while colour is a matter of individual taste, generally speaking, the most desirable is a strong sky to robin egg blue. Whatever the colour, for many applications, turquoise should not be soft or chalky; even if treated, such lesser material (to which most turquoise belongs) is liable to fade or discolour over time and will not hold up to normal use in jewellery.
Turquoise is consider a medium-soft stone especially in jewelry industry. Its hardness range from 5 to 6 Mohs. They are suitable for occasional jewelries, but not for daily use.