Diopside belongs to the monoclinic pyroxene mineral category. It forms a series of complete solid solution with hedenbergite (FeCaSi2O6) and Augite, but only partial solutions with Pigeonite and Orthopyroxene. It typically forms dreary green crystals of varying intensity of color belonging to the prismatic monoclinic group.
As is characteristic of the Pyroxene series It displays two separate prismatic cleavages, one at 93 and the other at 87 degrees. Vickers hardness is 7.7 and specific gravity is 3.25 -3.55. This mineral has a transparent to translucent configuration and a refraction index of of nα=1. 663 to 1.699, nβ=1. 671 to 1.705, nγ=1. 693to 1.728. The optic angle measure 58° - 63°.
Derivation of Name
Diopside gets its name from the Greek “dis”, "twice", and òpsè, "face" indicative of the two ways of orienting the vertical prism. It was first illustrated around 1800.
Diopside occurs in ultramafic igneous rocks of Peridotite and Kimberlite. You can find Aaugite, rich in Diopside in mafic rocks, like Andesite and Olivine Basalt. You can also locate Diopside among Metamorphic rocks that are in close contact with metaphorsed skarns that form Silica Dolomites.
The gemstone Diopside occurs in two structures: the chrome Diopside (which is inclusive of chromium, providing it with affluent green coloration) and the black star Diopside. Its hardness number is 5.5 to 6.5 on the Mohs scale; the chrome Diopside is comparatively soft when rubbed. Manganese-rich Diopside is Violane, which has a pale blue to violet coloration.
Diopside is found as gemstones in Canada, Russia, Brazil, South Africa and extensive range of various regions. The Chromium variety of Diopside is located in the regions of the serpentine belt in Northern California in the US, in Kimberlite in the Iron Mountain territory, in the Wyoming-Colorado State Line territory in Kimberlite, in Lamprophyre in Wyoming at the Cedar Mountain, protrusion of the Tertiary Bishop Conglomerate situated in the Green River Basin in the State of Wyoming and in the various anthills.
Diopside, an ancestor of white asbestos or Chrysotile as a result of magmatic differentiation and hydrothermal alterations, reacts on heating to 600 degrees C for 72 hours with magnesium and chlorine’s hydrous solutions to produce chrysotile. Vermiculite deposits, particularly In Montana and Libby, show deposits of vermiculate occurring from Diopside. At high temperatures you find a miscibility gap between Pigeonite and Diopside, while orthopyroxene and Diopside show the same features at lower temperatures.
It varies from light to dark green, gray, purple, light blue, yellow and white and can also be green having thin white streaks running though it, but seldom multicolored or colorless