About Calibrated Gems

Table of Contents

About Calibrated Gemstones.
Frequently Asked Questions About Gemstone Sizes.
Why use calibrated gemstone sizes in jewelry?
Why isn't the carat weight most important in jewelry design?
Why not define the size of jewelry strictly by gem carat weight?
Why are gemstones calibrated in metric units?
 Answer: Economics and to save time.

Calibrated gemstones (not a new concept) came into play long ago due to a gemstones specific gravity or density (a materials weight per its size). Every gemstone material varies as they have their own unique specific gravity. In short different materials have different weights such as a block of marble and the same size block of wood.

Lets compare two gemstones. A ruby with a density of 4 and an opal with a density of 2. A Ruby weighs two times as much as an Opal of the same size. Therefore the opal will be twice the size of a ruby at the same weight.

Let's look at a one carat opal and a one carat ruby. We can now see the opal will never fit into the same mounting the ruby is in. The opal, being lighter in weight than the ruby, would be twice the rubies size. We will need a different mounting for each gemstone of the same weight.

1 carat opal/1 carat ruby visual comparison.
There are many gemstones in the world, over 3000, and all of them vary in weight. Custom metal work is required if carat weight is used to define the size of the piece of jewelry for each gemstone. This would add a great deal of time and cost in producing each piece of jewelry. So gemstones and cast mountings are calibrated to save all of us cost and time.

Why use metric units. See our Gemstone information pages and view some of the  gemstones major sources. You will find many, if not most, gemstones do not come from the United States. We all know that most countries in the world use metric units. Gemstones come from many countries so metric units are used  in gemology as well as jewelry. The best we can do is to convert to English units as close as possible.