Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
First time I heard of a Congo Cube. Thanks Thomas.
Is the coating diamond as well? Looks like a secondary crystallization. Why are all the diamonds exhibiting this secondary crystallization? If the coating is diamond, it appears that they are all randomly oriented.
I was talking to someone who collected diamond crystals at Tucson, and he called these "sugar cubes" and said that occasionally they had a clean octahedron inside them. He actually had one there where the octahedron was exposed.
Can't really explain it. He had an example: a clean octahedral diamond surrounded by what looked like "sand" made out of diamond. The shape of the exterior is a cube. He told me they were called "sugar cubes" and they certainly looked like it. He said that sometimes when you dig into them, there is a clean octahedral diamond in them, and he had one with the edge worn away, where you could see the octahedral diamond crystal inside. if you go here: http://whistleralley.com/polyhedra/cube10.gif you can see how cutting the corners off a cube leaves an octahedron. (and you can go the other way, too.)
Here's a couple more from the same Kasai river alluvial Congo location. At about a hundred bucks a carat, would be nice if they were cuttable to any size.
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