Gem Cutting Acronyms And Meanings, and Advanced Cutting Techniques For Cabs

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Gem Cutting Acronyms And Meanings, and Advanced Cutting Techniques For Cabs

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The International Gem Society had 2 articles on cutting that I thought y'all might find interesting, and since they're related I'm going to put them both here. Since they both appear to be by Don Clark, and he gave me permission to repost his articles years ago, I"ll post the first one in its entirety, and the more extensive one you can use the link to access. Enjoy! :)

Gem Cutting Acronyms And Their Meanings

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The gem cutting acronyms found in facet diagrams stand for specific ratios that should help the jeweler determine if the design will fit a piece of rough. Some of the ratios refer to facets or faces of the finished gem, such as crown, pavilion, and table. “Facet Names” by Donald Clark.

"Question

I see gem cutting acronyms like L/W, C/H, and P/H in faceting diagrams. I’ve also seen TCP and PCP in some manuals. What do these terms mean?

Randy

Answer


L/W is the “length to width” ratio. This is an important bit of information included in many designs so you can get a good idea of how they will fit your rough before you start cutting. For example, if you had a 7 x 5 mm oval cut, it would have a length to width ratio of 1.4 (or 7 divided by 5). You couldn’t use that design for an 8 x 6 mm stone, because it has a L/W ratio of 1.33.

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A zircon cut to a 1.4 L/W roval design. “1.40 Roval (MC37.JRG)” by Jeff Graham.

C/H and P/H stand for “crown to height” and “pavilion to height.” This information will tell you if your rough is deep enough to cut the design. You may also encounter gem cutting acronyms like H/W, “height to width,” T/W, “table to width,” and T/L, “table to length.” These will help you get a better idea of how the stone will develop.

The instructions to “cut to TCP” and “cut to PCP” are from meetpoint cutting. TCP means “temporary center point.” PCP means “permanent center point.” A temporary center point is cut to give a reference point for the next sequence of facets. You can find detailed explanations of these terms in Introduction to Meetpoint Faceting by Long and Steele."

Happy faceting,

Donald Clark, CSM IMG


Access the article and sub-links here:
https://www.gemsociety.org/article/gem- ... -meanings/


Advanced Cutting Techniques For Cabochons
by Donald Clark, CSM IMG

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Both novice and experienced gem cutters can explore cabochons by taking leftover gemstone rough and cutting fancy shapes, functional pieces, or simply imaginative objects. In this unique pendant, a peridot cabochon caps a brass faux watch hand, lucite and wood flowers, and a vintage watch face with an enameled brass backing. “Dhalia Set: Peridot on Time” by viviannedraper is licensed under CC By 2.0

"There are many kinds of lapidaries. Some gem cutters are content keeping their family in birthday and holiday presents. Some find fulfillment putting the most intricate cuts on cubic zirconia. Still others only cut stones they’ve personally found. Some of us consider ourselves serious gem cutters. Our goal is to facet the most beautiful gems possible and make the best use of the material nature provides us. However, we often fall short. Over the years, most of us have assembled a large collection of leftover rough. This consists of our not-so-exciting material. We haven’t found the inspiration to cut these pieces, but they’re still too good to throw away.

Practicing cutting cabochons, particularly with advanced techniques, is a great way to use those seconds that have been lying around too long.

Combinations And Cabochons Can Re-Kindle Your Imagination

The secret to advanced gemstone cutting is using your imagination. You may have cut hundreds or even thousands of ovals. For a change, try a fancy shape or maybe something functional like a cord pull, drawer handles, a recipe card holder, or some ear jackets.

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Cabbing gemstones into practical items like this recipe card holder can help faceters flex their imaginations.

When choosing a cut for a piece of rough, don’t just look at its shape. Imagine how it will be used. Knowing if a piece is going to be used for a ring or bolo helps your cutting decisions. For example, sharp ridges on a ring stone would be vulnerable to impact and a poor choice. You can either avoid using that rough or find another use for the stone. This investigative process can lead to new ideas. You may come up with a broach or pendant design for your ridged stone you may not have thought of otherwise.

Some stones may look useless by themselves. Think about how they can be combined with other gems to make something useful. For example, long tourmaline crystals may be too thin to facet. However, they make excellent baguettes to accent other gems. This pink tourmaline started off measuring 12.3 x 3.3 x 2.1 mm deep. It was far too thin to facet, but look how nice it goes with blue apatite. I had this piece for years because it just didn’t inspire me. Once I matched it with other stones, it only took five minutes to cut it and create a stunning piece of custom jewelry. Combining gems is one of the best imagination exercises you can do. Comparing shapes, colors, sizes, and textures will help you find combinations you would otherwise have missed. This applies to both gem cutting and jewelry design.

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Pink tourmaline and blue apatite gems

If you have a lot of small gems and little inspiration, try turning them into cabochons. A quick and simple dome can turn a wasted piece of rough into a useful gem. If matched in size and color, a bunch of cabbed domes can be used in a cluster. You can turn your junk into something valuable in five to ten minutes.

(Our article, “Fundamentals of Lapidary Part 4,” has information on how to cut cabochons on a faceting machine).

Fancy Shapes For Cabochons ... "

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PinkDiamond
ISG Registered Gemologist


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