About Cabochon Carat Weight

by Millie from Gotrocks.

cabochon carat weight

Comparing carat weight of two 30 mm x 22 mm x 7 mm cabochons - orbital agate (left) and mookaite (right).


Since I’ve received more than a few questions about the carat weight of stones, I thought it might help to provide information about the subject.

In general the question asked most often is: “How many carats is a 30mm x 22mm (for example) cabochon?”

I assume that since there are many new people joining the jewelry making scene that is why the question keeps coming up.

The answer is – it depends:

  1. There is density or hardness (Mohs Scale) to consider, because we aren’t talking about diamonds here. A porous stone will weigh less, even though it is the exact same calibrated size.
  2. The thickness of a cabochon has to be considered. Most cabochons or focal beads are in the 5mm to 7mm range.

The two cabochons shown here are exactly the same size – 30mm x 22mm x 7mm.

The orbital agate carat weight is 37.8 cts. And the Mookaite is 36.4cts.

For new jewelry designers, here are a couple other items that seem to be confusing:

  • Cabochons for the most part are not drilled. Cabs are normally flat on the bottom and domed on the top. Cabochons can be double domed, in other words, the edges are rounded. Double domed cabs are great for wire wrapping, not good for bezel settings.
  • Calibrated sizes are standard sizes such as 30mm x 22mm or 40mm x 30mm. If a cut stone isn’t a standard size it is considered a freeform.

When you spend your hard earned money buying stones, don’t ever hesitate to ask a question about what you are buying.

Overstocked with Rocks
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