Gem Cutting Acronyms And Their Meanings


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

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

“Lapidary” by Lenore Edman is licensed under CC by 2.0
“Lapidary” by Lenore Edman is licensed under CC by 2.0