There are many factors that determine the price of precious or semi precious stones. When purchasing gems, it is essential to be aware of these factors. The most typical ones are color, clarity, carat and cut. These factors always play a role in the price of a gemstones although some of them have a greater effect than the others. How much these factors influence the price depends from precious stone to precious stone. The internet is full of web pages that deal about all the properties of the different sorts of gemstones. For the most well-known gemstones it's not difficult to find out all you have to know to make a well educated purchase. You can compare all the different gemstones that you have you fascination and if you read all the information offered on the internet you will know everything you need to know to make an informed purchase.
Different varieties of gemstones have a different price range. This has to do with the rarity of the gem in particular. The rarer the gemstone the higher the price will be. On top of that you have to factor in the perception factor. Some varieties are lower in price because they are readily available, because the color is not very popular (brown and yellow stones, for example) and some others because the material is relatively soft or even because they have all the right stuff but no one knows it. Just be sure to be well informed before buying gemstones. There is enough information available on the net.