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GeneralIs this fluorite fake?
13th Feb 2020 18:57 UTCProdromos Nikolaidis
13th Feb 2020 19:33 UTCKevin Conroy Manager
13th Feb 2020 19:36 UTCPaul De Bondt Manager
13th Feb 2020 21:56 UTCPaul Brandes Manager
14th Feb 2020 17:37 UTCEd Clopton Expert
Fluorite can and does form octahedral crystals, but the faces of cleaved and naturally grown crystals each usually have characteristic features not found on the other. Look at the faces of the natural crystals in the Fluorite gallery, https//www.mindat.org/gm/1576, and compare with the faces of your octahedron.
Cleavage in mineralogy refers to a tendency of many minerals to split more or less cleanly along natural planes of weakness in the crystal structure and can be a useful identifying characteristic. In general, cleavage planes coincide with possible crystal faces for the mineral in question. A particular cleaved crystal did not necessarily show that face--you can cleave an octahedron out of a cubic crystal of fluorite, and you can cleave a cube out of an octahedral crystal of galena--but other crystals of that mineral species could form crystals with faces parallel to the cleavage planes that produced the cleaved form.
15th Feb 2020 09:22 UTCProdromos Nikolaidis
15th Feb 2020 09:43 UTCFrank K. Mazdab Manager
15th Feb 2020 09:24 UTCProdromos Nikolaidis
15th Feb 2020 14:05 UTCKevin Conroy Manager
16th Feb 2020 14:27 UTCRolf Luetcke Expert
17th Feb 2020 16:54 UTCProdromos Nikolaidis
17th Feb 2020 19:14 UTCFrank K. Mazdab Manager
It's simply a cleavage, and a human took advantage of the 4 intersecting cleavage directions to form it into an octahedron. It's no different than buying a big cleavage of Iceland Spar calcite, another common museum gift shop curiosity, and someone taking advantage of its 3 intersecting cleavage directions to make it look like a nice rhomb.
What I'd like to see, and would even consider buying, is a masterfully-cleaved decent-sized dodecahedron of massive sphalerite. But such an item I've never seen at any mineral show or gift shop. One would think the transparent Spanish material would make an attractively cleaved curio, but maybe dealing with 6 intersecting cleavages is too many to control well?
17th Feb 2020 17:42 UTCKevin Conroy Manager
17th Feb 2020 18:11 UTCDavid Von Bargen Manager
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