Stunning sky blues, striking sea greens and rich robin's egg shades make turquoise a very desirable gemstone. Turquoise is almost always cut en cabochon or as a bead. It is seldom faceted. The dark and sometimes coppery-coloured veins are part of the beauty of turquoise and the smooth cabochon cut serves to showcase these distinctive features. Turquoise may be the first stone ever mined. There is some evidence that suggests it may have been mined as far back as 4000 B.C. It is a 5 - 6 on the scale of hardness, but its porosity presented real challenges in the past, as turquoise changed colour with time and wear. Today's gemstone treatments help alleviate that problem. The name, "turquoise," is relatively new to this blue stone. Pliny the Elder referred to it as callais from the Greek meaning "beautiful stone." It's thought that the name turquoise came into use somewhere around the 13th century.