How Do I Have a Gemstone Tested?

To see if it is geniune? I recently bough a cut blue sapphire on EBAY, from a dealer who has an excellent reputation. I paid a very low price, and the stone is beautiful-clear and a perfect light blue color. The cutting is flawless-no incorrect cuts or chip-outs.
So, is the stone real? can I take it to a jeweler for testing?
suppose it turns out to be a synthetic-was i ripped off?

Yes, you can have it tested. Can’t see where you are, but find a jewelry store that has somebody on staff with a certification from the Gemological Institute of America (are you in America? if not, there likely is an analogous association wherever). Synthetic sapphires are not terrible things, but if you were misrepresented, you should get your money back.

If it has no inclusions it is almost definitely man made - any jeweler could tell you with a loupe.

To be clear if it is synthesized, it isn’t any less of a sapphire. Chemically/physicially, it’s completely a sapphire. It’s just not mined.

Different from, say a CZ or Moissanite, which is NOT a diamond chemically (hence they are known as “diamond simulants”).

Shouldn’t a sapphire be dark blue?

A synthetic sapphire is real. Whether it’s less valuable is something for you to decide.

Sapphire can be any color at all other than red, and the only reason it can’t be red is that if it is, we call it ruby instead. Pure sapphire is colorless; the colors all come from various impurities.

Take a look at this bracelet to see various shades of sapphires.

One of my college teachers collected rocks. He had a quite-large star sapphire, part white, part light blue. It was just gorgeous.

Another clue that your stone is man made is if it is a bright blue (like this cultured sapphire, for example. As is apparent from AudreyK’s link, mined sapphires are normally in the steel blue -> navy blue range. Really bright blue stones are rare and valuable.

Sorry, I missed the edit window. A natural sapphire of comparable color is $800 for 0.64 carat, as seen here:
http://www.thenaturalsapphirecompany.com/Sapphires/Blue/

Moissanite is a rare mineral form of silicon carbide. It exists naturally (it’s more rare than diamonds) as well as synthetically created.

True but all jewelry-sized stones are manmade. Natural crystals are minute.

And most moissanite jewelry isn’t billed as real moissanite, but as fake diamond.

Of course, there’s also such a thing as genuine synthetic diamond, and depending on the circumstances of their manufacture, they can be more valuable than the natural ones. For instance, there are companies that will extract the carbon from a person’s cremated remains and process it into a diamond, which would surely have great sentimental value for anyone who would have one made.

A small note caution:

If an average kind of person wanders in to an average kind of jewelry store and presents a flawless sapphire, the jeweler is likely to pronounce the stone synthetic simply on the assumption that such a person would not be likely to have such a perfect natural stone.

If an obviously wealthy person goes in to a very high-end jewelry store and presents the same flawless sapphire the jeweler would want to have an appraisal done by a gemologist.