Amethyst is a transparent form of quartz that is one of the most popular and expensive variations seen in the market today.
It is mined in Zambia and the Latin American countries of Brazil , Uruguay and Bolivia . It may cost as little as a few dollars per carat and as much as $100-$150 per carat, depending on its size, quality and cut. The usual price range is $10-$100 per carat for anything smaller then 5 carats, $15-$115 per carat for anything between 5 and 10 carat weights and $25-$150 per carat for 10-25 carat weight gems. It is a hardy stone, rating 7 on the Moh scale and it is a cheap, available option for nice-looking jewelry pieces. Easily found in very large pieces, this stone comes in a range of purple colors, ranging from the palest lavenders to dark purple. The most expensive amethyst color is the intense, evenly-toned purple that flash of red under incandescent light. The least expensive is the kind with the least color- pale lavender quartz with very few undertones and no depth to the color.
The color in quartz should be permanent if the stone is kept indoors and away from heat, but beware of exposing it to the climate. In general, it is a durable stone that can be safely cleaned in most ultrasonic cleaners if it's not fractured. However, care must be taken; delicate in nature, amethyst may fade or change tonality under steady sunshine or if placed too closely to the fireplace. As with almost all the gems today, it is also being imitated and simulations flood the market periodically. If you are buying a particularly large piece, send it to be tested, and if the color changes despite the care you have given it, take it back to the store to be examined.