Gems

I started with the official D&D information and expanded on it.

Standard gems carried by adventurers are 1/4″ in diameter. They are carried in small leather or cloth bags tied securely with a string or leather strap. Unless your character is carrying an extremely large number of gems, their weight is insignificant and you do not have to keep track of it. The information listed here is provided for those rare occasions when your character may need to carry an exceptionally large gem or a very large number of gems.

In the real world, gem sizes do not determine weight. The density of gems varies from very light stones like opal to especially heavy stones like sphalerite or zircon. To keep it simple for D&D I am keeping the weight of all gems the same and only vary the value depending on gemstone type and size. The price per carat does not increase smoothly with increasing size. (One 4 carat gem is more valuable than four 1 carat gems.) To allow for larger stones in my game they don’t increase quite as fast as they do in the real world. I justify this by saying that larger stones are not as rare in my world.

All gems listed here are round faceted and have the same depth as their diameter making them roughly spherical (think 20 sided dice).