Turquoise is a gem that has a characteristic blue hue and is often browsed by matrix (black streaks). Turquoise was brought from Persia by Turks that sold them to Europeans. Western people were very keen on this gem of pure and unique blue shade, and called it mistakenly "turquoise" that is "stone from Turkey". Persia (actual Iran) still produces the most beautiful turquoises, thanks to it deposits from the Nishapur area. Iranian turquoises are absolutely flawless, without any matrix. That's why a lot of imitations have been evolved to look like those amazing turquoises. Turquoises with matrix, for most of them, come from the U.S, but you can also find some in Afghanistan, Nepal (for the green ones), and in South America.