Guest Post - Reprinted with the permission of the author...
Many people come to me looking for a certain carat "size" of gem, but they don't realize that often this is not the best measure to tell whether the gem in question will work for their project or not.
Since carats are a measure of weight and not a measurement of visual size they can be misleading. Imagine looking for a one pound block of wood or a one pound block of steel. They both would weigh the same, but the block of wood will LOOK far larger because wood is less heavy than steel.
Since carats are a measure of weight and not a measurement of visual size they can be misleading. Imagine looking for a one pound block of wood or a one pound block of steel. They both would weigh the same, but the block of wood will LOOK far larger because wood is less heavy than steel.
When you are choosing a gem it is very important to consider the millimeter size since the varying densities of different gem materials and also the varying depths of different cutting styles can result in a significantly different “face” size, even between gems with a similar carat weight.
Millimeter (mm) size is far more important for practical purposes than the carat weight. You want to know the carat weight because your friends (or customer's friends) will ask. But you need to understand the mm size so you know if a particular gem will work for the design and style you want.
So it is very important that you get a feel for MM sizes and what they mean in visual and practical terms.
Also keep in mind the shape of the gem, some shapes will look larger even if they have the "same" mm size. See example below.
Due to screen resolution, etc. the image is not actual size. But it serves to illustrate what we are talking about.
For a more complete version of this article and printable PDF's with rulers, explanations and other useful guides to choose the right size gem please go to: http://www.johndyergems.com/MM-Size.html
Have fun finding just the right gem for yourself!
John Dyer
www.johndyergems.com