Sphalerite is the most outstanding Spanish gem material. Aliva mine in Cantabria produced the world’s best and largest transparent toffee-colored sphalerites, well known worldwide among collectors of rare gems and minerals. Spectacular faceted Spanish sphalerites can be found in museums and private gem collections all over the world. 

The mine was closed in1989 and the area was declared a National Park. All Spanish faceted sphalerites on the market come from the old stock material. The mine was very productive and mineral dealers and collectors still have some pieces that occasionally show up on the market.

Sphalerite is a soft stone. Its hardness is only 3.5-4 on Mohs scale. That’s why it is normally not used in jewelry. It does have however both a very high refractive index and an extremely high dispersion, making this gem an extraordinary piece for collections.

precision cutting

Precision cutting, also called custom cutting, is a combination of faceting techniques and machinery facilities which allow us to cut the stones using original faceting designs, created by special computer programs, and to get spectacular results in precision of angles and symmetry of the stone, together with exceptional polishing quality of the facets. Prior to the faceting, the light trace inside the gemstone can be modeled on computer, and angles of the crown (upper part) and pavilion (lower part) adjusted especially for the refractive index of the gemstone, to optimize its brilliance, scintillation and dispersion. In standard commercial cutting, the lapidary usually tries to save as much weight of the rough stone as possible, with little care of angles and brilliance of the stone. The quality of polishing and symmetry in mass-produced stones is also normally quite low.

Available gem sphalerites

I regularly upgrade the list of available sphalerites, classified by weight categories. Some other sold stones can also be seen in corresponding sections.

The colors of Spanish sphalerites range from dark orangey red, through orange and yellow to yellowish green. The dispersion is much better observed in lightly colored yellows and greens, in darker stones it is hidden by the body color. Also, for dispersion it is much better to use punctual light sources, like led spots or direct sunlight. Diffused light, like in a cloudy day, hides the dispersion.

Gem quality sphalerites are also produced in Bulgaria, in the area of Madan ore field. The colors of Bulgarian sphalerites are slightly different, they can have a pure green color in some rare cases, but never produce pure intense oranges as Spanish stones. I also cut Bulgarian sphalerites, they can be found in corresponding sections of the site.

Sphalerite is a soft stone, it must be handled with care. I do not recommend to use steel tweezers with sphalerite.