Final answer:
Kunzite and hiddenite are different gemstone varieties of spodumene, distinguished by their colors—kunzite is pink to violet, and hiddenite is green. Their colors are due to impurities of manganese and chromium or vanadium, respectively.
Step-by-step explanation:
Kunzite and hiddenite are varieties of the gemstone spodumene, which is a silicate mineral. The primary differences between them lie in their color and the impurities that produce these colors. Kunzite exhibits a pink to violet color and owes its hue to the presence of manganese, while hiddenite is green due to the presence of chromium or vanadium. Both are prized for their clarity and vivid colors and are used in jewelry.
Examples of other minerals associated with metamorphic rocks include garnet, kyanite, and staurolite. Gem-quality crystals like ruby and emerald also gain their color from chromium impurities, similar to hiddenite. It's important to recognize the conditions under which these gems form, such as the pressure-temperature conditions indicative of certain geological terranes.