The most amazing thing about collecting coloured gemstones is that Mother Nature never fails to shock you. Until February 2009, all I knew about Sphalerite was that the Smithsonian Museum of Natural History and the Liverpool World Museum had samples of this mineral; I had never contemplated setting the mineral in jewellery and had therefore not written about it before.
Then over dinner one day, a very good friend of mine told me he had recently seen a specimen that was bright orange and that it had an amazing amount of dispersion. The next day I spent several hours on the internet researching the gem type and was amazed at what I found. My friend’s observation of a strong amount of fire was very accurate indeed: the gem has a dispersion that is over three times that of a Diamond (technically speaking it has a B-G interval of 0.156)!
Sphalerite consists mainly of Zinc and Iron. Normally the Iron content dominates and the mineral looks similar to the dull pieces seen in the museums. Most Sphalerite is opaque and black and is sometimes referred to as Marmatite (was this the origin of our Marmite spread or was it a French stew?). Isn’t the gem world so exciting, when the graphite in your pencil has the exact same chemical composition as a Diamond (see allotropic) and dull old Marmatite is the same mineral as the most incredibly dazzling and monumentally rare Sphalerite! To my knowledge only a handful of yellow, orange and red specimens have been found so far.
Only two mines have ever been reported to discover gem quality pieces; the Chivera mine, in Sonora Mexico and the Las Manforas Mine in the Picos de Europa Montains (the first national park in Spain) located on the North Coast of Spain near Santander. Its name is derived from the Greek word for ‘treacherous rock’, as non-gem quality specimens can easily be confused with other minerals. The gem is also known as Blende which is the German word for ‘blind’ (most likely so for the same reason as the Greek meaning).