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Prices change, and you need to say what server you are on.
Depends on the particular purplish crystal. Amethyst is not too expensive but other purplish crystals expensive. So it depends.
no
Yes,the crystals are so big to earn money
Highly variable, depending upon size, quality, locality, etc. A small, damaged druse of crystals from Mexico might fetch $10, a superb cabinet specimen with large perfect crystals from Sicily might fetch thousands.
Crystals are about 12 dollars.
Swarvoviski crystals undergoe strenuous testing and therefore usually cost more.
loads
A rock with large crystals scattered on a background of much smaller crystals is called a porphyry. This rock texture is the result of two stages of cooling, where large crystals formed during the slower cooling stage, followed by smaller crystals forming during rapid cooling.
Well the formula is CuSO4
A couple of packets of Ramen noodles. But seriously, it depends on the quality of the stone (e.g. clarity, color, crystal shape if any, etc.)
Not much except for the fact that the hard crystals may scrape off more plaque. Other than that not much.