A large number number of gemstones were known to many cultures during the medieval period. Which gemstones were known in which time and place is harder to ascertain. Such small precious goods could travel vast distances via trading, a trade which had been widespread in the time of the ancient Myceneans (2000BC?), so it is only via the evidence of archeological finds and writings of gemstones that we can be sure which stones reached which cultures. Trade goods were more likely to reach prosperous outwards looking cultures than ones undergoing war, famine or internal unrest.
Books on gemstones, called lapidaries, were published throughout period. Many names occur for the same gemstones in medieval literature, making it difficult to identify the gemstone named. The same name may also be applied to several similar looking gemstones, e.g. carbuncle could refer to ruby or garnet.
Types of Gemstones
These are the four traditional precious gemstones:
NOTE: The price of these stones depends upon the 4 Cs; color, clarity, cut, and carats (weight). A large heavily included specimen may be much cheaper than a small but otherwise flawless stone.
Moderately Expensive Gemstones
- amethyst (bigger discoveries in the modern period have brought the price down, making it a good value choice for the modern reenactor)
- citrine (natural citrine is a pale yellow color and rather expensive. Most citrine on the market today is heat-treated amethyst or smoky quartz. The color ranges from amber to golden red)
- garnet (depending on type; rhodolite and pyrope are moderately expensive, but almandine is fairly cheap if one knows where to shop)
- zircon (also known as jacinth)
- cornelian or sard
- rock crystal (see entry on quartz)
- moonstone (again, price varies as to type; adularia can be rather expensive)
- amazonstone (but see Cariadoc's entry on eumentres)
- black opal
- jade (not available in Europe, rare in the Middle East, common in China)
- tiger eye (http://www.pbm.com/~lindahl/cariadoc/gemstones.html)
Also fake gemstones (e.g. Cabochons - coloured glass jewels backed with metal foil) existed in medieval times, as a cheaper way to make things more ostentatious. They are more likely to be used in uses such as garments and belts, than on something like the crown jewels. Just remember that in some times glitz was popular, with more being better, but in others obvious use of fake gems would mark one as a cheap try-hard, and a few fine pieces of real gems might be preferred. Enamel could also be used to create brightly coloured blobs that pass for gems at a distance.
See also: Imitation Gemstones