Apophyllite-(KF) or fluorapophyllite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

of the

apophyllite The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that compris ...

group, with the chemical formula of KCa₄Si₈O₂₀(F,OH)·8(H₂O). It gets the first half of its name, "fluor", from containing more fluorine than

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...

compared to the other minerals in the apophyllite group. Fluorapophyllite crystallizes in the

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...

crystal system. Tetragonal minerals have three axes of different lengths and angles of 90 degrees. Fluorapophyllite is an anisotropic mineral and has low relief. This mineral belongs to the uniaxial (+) optical class, which means its indicatrix has a prolate sphenoid shape with a circular section, principal section, and one optic axis. Among the apophyllite group, fluorapophyllite is the most abundant compared to the other two minerals in the group, hydroxyapophyllite and natroapophyllite. It is popular among many mineral collectors because of the large, well-developed crystals they form and the multiple colors they come in. The most wanted variation of fluorapophyllite is the green colored variant, which is found in India. Fluorapophyllite is also found in New Jersey of the United States.Cook, Robert B. (1995) Fluorapophyllite. Rocks and Minerals, 70. 394-398. This mineral is found as a secondary mineral in

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...

s such as

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

Images

File:Fluorapophyllite-Stilbite-Ca-indi-94b.jpg, Stilbite crystals surround a pastel green, translucent fluorapophyllite crystal File:Apophyllite-(KF)-66684.jpg, Isolated apophyllite cluster on contrasting matrix File:Apophyllite-(KF)-131740.jpg, A radial cluster of cubically-tipped apophyllite crystals File:Apophyllite-(KF)-Stilbite-Ca-Calcite-171681.jpg, Light green form from Pune District, Maharashtra, India

References

{{commonscat, Fluorapophyllite-(K) Phyllosilicates Tetragonal minerals Minerals in space group 128