If you want to make sure you're amethyst is real, look for a solid dealer. You're less likely to find knock off amethyst if you work with a dealer with a solid reputation.  Ask friends who are into jewelry. This is the easiest place to start when seeking out a gem dealer. If you have friends that have a lot of expensive jewelry, ask them where they got their best pieces. They may be able to point you to a solid dealer. The American Gem Trade Association, the Federal Trade Commission, and the Jeweler's Vigilance Committee are organizations that all work to ensure honestly and quality when it comes to gem dealing. If a jeweler is affiliated with one of these organizations, he or she is more likely to be legitimate. If a gem comes with a lab report, which should verify things like specific gravity and hardness, it's far more likely to be authentic. Buy from dealers who provide lab reports with their gems. A reputable dealer should not shy away from answering questions about his products. Ask where the amethyst comes from. If the dealer hesitates, this is a bad sign. A good dealer should be knowledgeable about the origin of his products.  Amethyst is typically found in Brazil, South Africa, and Namibia. In the US, it's often found in Arizona, Colorado, and the Carolinas. It's also found in parts of Canada.  If a gem does not come from one of the above places, that does not necessarily mean it's inauthentic. Amethyst is present across the world. However, request a lab report if the amethyst is from an unusual region. Amethyst is generally inexpensive. It's not uncommon to find amethyst jewelry for around $20. You should be suspicious of amethyst sold cheaper than this. Many vendors may market fake amethyst as authentic and then sell it well below market value. This is to trick consumers into thinking they're getting a deal. Follow the old adage, "If it seems too good to be true, it probably is." Stay away from low price gemstone. When buying amethyst, ask for information about where the gem was mined, how it was cut, and so on. If a jeweler is able to answer these questions with ease, his product is more likely to be authentic. If he seems hesitant to provide too much information, he may be hiding something. It might be a good idea to seek out another seller. Many stores mislabel synthetic stones or low-quality purple sapphire as special forms of amethyst. They may be marked as Japanese Amethyst, Desert Amethyst, Lithia Amethyst, or Bengal Amethyst. Be distrustful of such designations. These stones are likely fake. It's not recommended that you purchase gems online. Fraud is far more likely over the internet. However, if you choose to go the online route, go for a site that seems legitimate.  The dealer should be affiliated with some of the organizations listed above. He or she should also have a company name, phone number, and physical address.  Check to make sure the business is active. New content should be added regularly. There should be information about how much of a given product is in stock.  Read any reviews you can find. If a lot of customers had a problem with a given store, it may have a bad reputation for a reason. You should also not buy amethyst online if there's no return policy.

Summary:
Find a reputable gem dealer. Ask about the gem's origin. Consider the price. Ask for information during the sale. Be wary of unusual names. Look for legitimate online dealers.