saussurite

Saussurite is a mineral aggregate which is formed as a hydrothermal alteration product of plagioclase feldspar. It appears very similar to zoisite with a green or grayish-green color, it has been used as a substitute or simulant for jade.

Saussurite is not however recognized as a true mineral because it is a microscopic mixture of several other minerals, zoisite, epidote, sericite, albite or other sodium-rich feldspar along with possibly scapolite. The use of microscopic refractive index data and X-ray diffraction patterns are needed to distinguish some saussurite simulants from true jade.