SEPM Strata


flourite
igneous rocks metamorphic rocks minerals sedimentary rocks	Description Fluorite gives meaning to the admonition Never Trust Color! Its color is extremely variable, as the next few specimens show. The most distinctive features are the Octahedral Cleavage, and the Hardness. The octahedral cleavage is obvious in these perfect specimens. It is the less than perfect specimens, or the intergrown crystal masses that can be troublesome. To identify find one crystal, and then carefully count the 4 cleavage directions. Also the cleavages form acute triangles, and is distinctively different from Cubic Cleavage in halite, or Rhombohedral Cleavage in calcite. Physical Properties CaF₂ Hardness = 4; Cleavage: Octahedral; perfect in 4 directions; Shape: octahedral, but often cleavage masses or masses of intergrown crystals masses Color: violet, blue, green, yellow, brown, bluish, black, pink, rose-red, colorless Luster: Vitreous (Glassy) Another Sample Description The clear, glassy properties of this specimen might confuse it with quartz (right). But look more carefully, and you can see cleavages cutting through the mineral (which quartz does not have). These cleavages also form acute angles, typical of the Octahedral type. And if you could rotate the specimen a little you would be able to count the four cleavage faces. Another Sample Description The color of this specimen is in sharp contrast with the last specimen, and just shows the variability. Can you detect in the image the octahedral cleavage? Another Sample Description Notice at the bottom of the crystal the acute triangle formed by the octahedral cleavage. Typical fluorite. Another Sample Description At first this massive green variety of fluorite might be confused with something like apatite, or olivine. hardness would help with olivine (6.5-7), but not apatite (4). But look more carefully, especially on the left side of the specimen, and you can see some cleavages passing through; they are octahedral, and diagnostic of the fluorite.