From Rough to Polished: How a Gemstone Is Cut

A rough gemstone is a proposition, not a product. The cutter's decisions — orientation, shape, proportions and finish — determine whether a crystal becomes an ordinary stone or an exceptional one.

Orientation comes first

Many gem species are pleochroic, showing different colours along different axes. Tanzanite, for example, can appear blue, violet or burgundy depending on direction. The cutter orients the rough so the finest colour faces up, even when that costs weight.

Yield versus beauty

A typical rough crystal loses between 50 and 70 percent of its weight in cutting. The temptation is to save weight with a deep or lopsided stone. Good cutting accepts a lower yield in exchange for proportions that return light evenly across the face of the stone.

The stages

1. Preforming — grinding the rough to a basic shape and removing inclusions that cannot be worked around.
2. Faceting — placing each facet at a precise angle on a lap wheel, from the crown down through the pavilion.
3. Polishing — bringing each facet to a mirror finish with progressively finer abrasives.
4. Inspection — checking symmetry, polish and light return under magnification before the stone is graded.

Why it matters when you buy

Two stones of identical weight, colour and clarity can differ by a third or more in price because of cut alone. When you compare stones, look at them in ordinary light and watch for dark or "windowed" areas — the signature of weight saved at the expense of beauty.

SOMSTONE's stones are cut by partners who work to our specification, and each is checked before it is offered.