chrome diopside and quartz are two different gemstones. Chrome diopside is sometime found along with quartz and hence the name.
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.
chrome diopside
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.
Yes, of course they are valuable. Check out ebay.
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.
"Violane", the manganese rich violet to blue variety of diopside, is quite uncommon, found in Italy, Greece, and California, according to mindat.org.
Chrome ore is usually for production of ferrochromium and chrome, which is widely used in metallurgical industry, refractory matter, chemical industry and so on. Chrome ore is one of the most valuable metal ore in the world. Chrome ore mining and beneficiation is an important industry in some countries such like Pakistan (Muslim Bagh) South Africa, and so on.
Examples: ruby, emerald, diopside, tourmaline.
They are no more valuable than any other rubles from other years. they are still the official currency of Russia.
Garnet, Almandine, Grossular, Andradite, Uvarovite, Diopside, Melanite, and Spessartine.