From: Kerr McGee Mine, Carlsbad, New Mexico, USA
Size: 4.7 x 7.3 x 2.9cm
Good blue halite specimens from Carlsbad are getting harder and harder to find since there hasn't been any mining there in years, so the supply has really become scarce. Luckily, we know a former employee of the mine who still has some excellent specimens in his posession, so we have been able to acquire quite a few exceptional pieces. There are basically two types of blue halite specimens that you'll see for sale: slabs and crystal cubes. The slabs are fairly inexpensive and much easier to find but still beautiful, but the crystal cubes like this specimen are what are most valued by collectors.
This specimen consists a 2.4cm long primary blue halite crystal along with several other smaller blue halite crystals on matrix with sylvite. The primary cube has excellent blue color and transparency. It also has an unusual shape in that some of the sides are not completely parallel to the other sides. They are not cleaved - the cube is in perfect condition, but it is just a result of unusual crystal formation.
The blue halite is chemically the same as the clear halite - the color is not caused by any additional chemical elements in the salt. The blue is actually a result of tens of millions of years of exposure to the radioactive potassium in the sylvite (Potassium Chloride). This is the same potassium you'd find in a banana, and it has a half-life of a billion years, but over tens of millions of years of exposure it builds up and the atomic modifications to the crystal structure are what cause it to appear blue. If you were to dissolve it and let it re-crystalize it would look white just like regular salt.
The specimen comes with a labeled acrylic display base.