"Violane", the manganese rich violet to blue variety of diopside, is quite uncommon, found in Italy, Greece, and California, according to mindat.org.
Most reports of chrome diopside are found in Libby, Montana. Though there have been reports of finding these kinds of diopside in Canada, South Africa, Russia and Brazil.
Yes, Russian diopside and chrome diopside are the same gemstone. Chrome diopside is a variety of diopside that is deep green in color due to its chromium content. It is often referred to as Russian diopside because it is primarily sourced from Russia.
chrome diopside and quartz are two different gemstones. Chrome diopside is sometime found along with quartz and hence the name.
Rarity is relative, and debateable. I think it's safe to say that diopside is not considered to be a rare mineral, though large, transparent green well-formed crystals of diopside are indeed rare, as are fine, large and clean faceted stones.
chrome diopside
Examples: ruby, emerald, diopside, tourmaline.
The cast of La Vision - 2006 includes: Violane Chavet Jim Eng Barbara Milot Sean Perham
Garnet, Almandine, Grossular, Andradite, Uvarovite, Diopside, Melanite, and Spessartine.
Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside
Gantz ,
The folowing stone gets there color from chromium or its traces. Chrome diopside, Ruby, Grossular Garnet, Hessonite Garnet, Jade,Chrome Tourmaline (Green Tourmaline),Greenish Turquoise Most stone from the Beryl family like: Morganite, Emerald, Chrysoberyl, etc.
Chlorine, like any other chemical substance, has no hardness unless it is in its solid state. Even then, a temperature would have to be specified for a meaningful answer.