|Pure color in turquoise is rare. The stone,
which ranges from light blue to gray-green, is usually interspersed with brown, dark gray, or black veins of other
minerals or the host rock. These interspersions are called turquoise matrix. American turquoise is marketed in
one hundred fifty two recognized shades of blue and green, with the robin's-egg blue varieties most commonly used
by southwest Indian silversmiths. Turquoise can have a waxy luster or matte texture.