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2. Fluorite - Wikipedia

   en.wikipedia.org/wiki/Fluorite

   Fluorite has four perfect cleavage planes that help produce octahedral fragments. [13] The structural motif adopted by fluorite is so common that the motif is called the fluorite structure . Element substitution for the calcium cation often includes strontium and certain rare-earth elements (REE), such as yttrium and cerium .

3. Cleavage (crystal) - Wikipedia

   en.wikipedia.org/wiki/Cleavage_(crystal)

   Rhombohedral cleavage occurs when there are three cleavage planes intersecting at angles that are not 90 degrees. Calcite has rhombohedral cleavage. Octahedral cleavage occurs when there are four cleavage planes in a crystal. Fluorite exhibits perfect octahedral cleavage. Octahedral cleavage is common for semiconductors.

4. Calcium fluoride - Wikipedia

   en.wikipedia.org/wiki/Calcium_fluoride

   Doped calcium fluoride, like natural fluorite, exhibits thermoluminescence and is used in thermoluminescent dosimeters. It forms when fluorine combines with calcium. It forms when fluorine combines with calcium.

5. Fluorite structure - Wikipedia

   en.wikipedia.org/wiki/Fluorite_structure

   Many compounds, notably the common mineral fluorite (CaF 2), adopt this structure. Many compounds with formula M 2 X have an antifluorite structure. In these the locations of the anions and cations are reversed relative to fluorite (an anti-structure); the anions occupy the FCC regular sites whereas the cations occupy the tetrahedral ...

6. Mineral - Wikipedia

   en.wikipedia.org/wiki/Mineral

   Octahedral cleavage (four directions) is present in fluorite and diamond, and sphalerite has six-directional dodecahedral cleavage. [ 80 ] [ 81 ] Minerals with many cleavages might not break equally well in all of the directions; for example, calcite has good cleavage in three directions, but gypsum has perfect cleavage in one direction, and ...

7. Extinction (optical mineralogy) - Wikipedia

   en.wikipedia.org/wiki/Extinction_(optical...

   Inclined extinction is a measured angle between 1-89 degrees. Minerals with two cleavages can have two extinction angles, with symmetrical extinction occurring when minerals have multiple angles that are the same. Minerals that have no cleavage or elongation can not have an extinction angle.

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9. Lustre (mineralogy) - Wikipedia

   en.wikipedia.org/wiki/Lustre_(mineralogy)

   Vitreous minerals have the lustre of glass. (The term is derived from the Latin for glass, vitrum.) This type of lustre is one of the most commonly seen, [9] and occurs in transparent or translucent minerals with relatively low refractive indices. [2] Common examples include calcite, quartz, topaz, beryl, tourmaline and fluorite, among others.