Used in jewellery for thousands of years, Moonstone is the birthstone for June and has a hardness of 6. Its captivating schiller is known as adularescence which is due to light reflecting from layers within the gem. Translucent to transparent Moonstones with a blue schiller are more valuable than the more opaque milky gems. It is sometimes seen in orange, green and grey tones, and occasionally Moonstone displays a cat’s eye effect known as chatoyancy.
Moonstone is a member of the Feldspar mineral group, it is doubly refractive with an RI of 1.520 – 1.525. The specific gravity of moonstone is 2.56 – 2.59. Fine quality Moonstone is found in Southern India, Sri Lanka, and limited quantities in Burma.