With a hardness of just 3.5 to 4, sphalerite can be scratched very easily. Common household dust, with a hardness of 7, would scratch sphalerite if you wiped it off with a cloth. Faceters also face additional challenges cutting this stone. It has six perfect cleavage planes in its isometric crystal structure and it’s brittle. It also frequently displays color zoning. As a result, you’ll find relatively few cut sphalerites, even though rough is available.

Careful, expert cutting and polishing can enhance this gem’s high dispersion or fire and take its luster to a bright, diamond-like adamantine. If sphalerites were tougher, they would probably be very popular, important gems.

Sphalerite Buying and the Four Cs

The IGS sphalerite value listing has price guidelines for faceted pieces.

Color

You’ll find that fine red or orange sphalerites, especially in sizes above three carats, command high-end prices. Generally, green, yellow-green, and brownish stones have lower values, as do smaller pieces of any color.

Colored gems with lighter tones typically display their dispersion to greater effect than darker stones. However, sphalerite has a refractive index (RI) that can range somewhat higher than diamond’s. Its dispersion also exceeds diamond’s famously high value over…