Boulder turquoise has a warm earthy look to it because it is Mother Earth with a ribbon of bright turquoise running through it – thus it is also sometimes called Ribbon Turquoise. The ribbon can appear and disappear in the mother rock.
Boulder Turquoise can be found in any mine, but often the rock surrounding the turquoise is too brittle or soft to polish into a cabochon or a stone for a setting.
Therefore, a few mines are noted for their production of usable Boulder Turquoise for jewelry: Pilot Mountain and Royston. Read More about US Turquoise Mines here.