Your eye is not a tool. Natural gemstones come in all colors, shapes, and sizes, but so do imitations and synthetics. No matter what you are told overseas, be sure to check it out with a knowledgable gemologist. Ask for some kind of certification regarding the gems you are buying no matter what you are spending, do not buy unless you are sure you know what you are buying. Be very careful because the laws governing business in foreign countries are usually not as strict as those in the U.S.
Gemstones are weighed in carats. There are 100 points in a carat. Likewise, 50 points equals 1/2 carat and 75 points equals 3/4 of a carat. Since gemstones are sold by weight, be sure the scale being used is giving you the accurate weight. Check that it is at zero before the gemstone is weighed. Do you know who you are buying from? This is the most important thing to consider when buying overseas. A street vendor may or may not be legitimate, so unless you are a risk-taker, buy from an established store with a referral from one of your buddies. If you buy out of the country, you are out of luck if something goes wrong, especially if you paid with cash or traded your american goods for them.
Quality
The rule of thumb with colored gemstones is the intensity of the color is the most important thing to consider. Gemstones that are too light or too dark are not ideal, and usually of lesser quality. When looking at a gem be sure it is transparent and that light is reflected because these gemstones are of higher clarity than those that are cloudy. Many gemstones are treated with radiation, dyed with chemicals, or filled with glass or lead to intensify the color and these are worth much less than non-treated ones.
Credit cards
If you can, use a credit card when you make a purchase. This allows you to get a refund from the credit card company if you find out later your purchase is not what you think it is. If you pay with cash, have as much information written on your receipt as possible. If there is a problem with what you bought, you can get the word out fast to your buddies so they are not also taken advantage of.
Pricing
Comparing prices on gemstones is a good idea as long as you are comparing apples with apples. Many characteristics play a part in the pricing of gemstones and it is up to you to decide which gem is the best deal. Cut, color, clarity and weight, all are factors considered in establishing the price. Remember, if it is too good to be true, then question it. Unless the price is unusually exceptional, it is better to buy in the United States from a reputable dealer than take chances in a foreign country.