Turquoise, Yellow Brown Matrix Turquoise BraceletWhat is the brown matrix in turquoise? Turquoise deposits usually form in iron rich limonite or sandstone. Limonite creates dark brown markings in turquoise, while sandstone creates tan markings. These markings are remnants of the host rock within the turquoise, and can resemble splotches or veins. They're called matrix. Yellow Brown Matrix Turquoise is a type of turquoise with striking yellow and brown matrix patterns, blending the calming energies