An amazing sapphire crystal
Mined in the mid 1990’s in a remote corner of the San Jacinto Mountains of California we have an opaque purplish brown corundum crystal in a perfect hexagonal barrel shape with two tapering terminations. The piece is large (14.1 x 7.6 x 5.8 cm, 13 cm for the crystal itself) and set in its metamorphic matrix, a once aluminium rich rock that was heated and squished in the depths of the Earth. Both matrix and crystal are fluorescent (as seen in the last photo), giving off light in visible lower energy wavelengths when excited and stimulated by higher energy and wavelength UV light as electrons in the outer shell of atoms absorb energy, jump up to a higher shell and drop back again giving off the remainder as light (see https://bit.ly/1GPmnMy for a more detailed explanation).
Image credit: Rob Lavinsky/iRocks.com