Fine mineral specimen: Fluorite crystal with quartz crystals, Yaoganxian Mine, Hunan Province China

The fine mineral specimen presented in this video is a pristine example of fluorite with quartz from The Yaoganxian Mine, Hunan Province, China. This small cabinet sized fine mineral specimen is 8.2 cm across.

This piece consist of a pristine and complete fluorite crystal on a matrix of colorless quartz crystals. The fluorite crystal is a pristine cube and with razor sharp edges and vertices. The fluorite crystal is complete and even when inverted, it can be seen that no part of this pristine mineral specimen is afflicted by cleaved corners or any contacting or cleavage faces. The most discriminating mineral collectors including Professor Stephen Smale (Fields Medal) look at mineral specimens closely for perfection after the “front view” of the piece engages them with fine esthetics and perfection. The fluorite crystal is mostly transparent with some veils along internal cleavage planes. The fluorite crystal is also colorful and displays purple phantom crystals close to the external crystal faces and is pastal green and blue in the rest of the interior. The presence of this piece is added to by the matrix of colorless quartz crystals. Matrix specimens of any type of mineral specimen are almost always more valuable when the matrix is also esthetic and when the size of the matrix is not out of “oversized” and hence out of proportion to “the rest” of the specimen.

The simple cube is the most common shape for fluorite crystals but despite the simplicity and abundance of this fluorite crystal morphology, cubic fluorite crystals and crystal clusters are among the most collected type of mineral specimen among private collectors.

As of July 2021, a total of 4866 mineral species were listed in “The Glossary of Mineral Species” published by “The International Mineralogical Association.” Most mineral species can only be appreciated under magnification with a microscope. Most advanced private collectors can recognize around 300 mineral species. All private collectors who are generalist collectors will own at least some fluorite specimens. Fluorite is the second most represented mineral species in “The Matthew Webb Fine Mineral Specimen Collection'” which is a generalist collection of esthetic worldwide display mineral specimens. Some collectors only collect fine fluorite specimens.

Fluorite is a popular mineral species because it occurs at thousands of localities all over the world and as esthetic specimens with distinctive and eye visible crystals and in a variety of colors that cannot be surpassed by any other mineral species. Fluorite crystals can be various shades of purple or violet, orange, green, blue, indigo, brown, pink or even colorless and water clear. Colorless fluorite is even rarer than pink fluorite. Fluorite crystals are normally simple cubes but when fluorite crystals deposit at higher temperatures, they are more likely to be either cube octahedrons (i.e. a cubic crystal with truncated corners), cubes with bevelled edges octahecrons, octahedrons with truncated tips, octahedrons with bevelled edges, docecahedrons (a polyhedron with 12 regular pentagonal faces), pyritohedrons (a polyhedron with 12 pentagonal faces but which are not all equal and more complex crystal shapes. Fluorite crystals can also be twinned. Some well known types of fluorite crystal twins include penetration twins and spinel law twins.

Fluorite is calcium difluoride and is water soluble at room temperature (40mg in 1000 mL) and is stable under a wide range of temperatures, pH values, redox potentials and in the presence of other dissolved mineral species. Hence, fluorite occurs in a wide variety of geological context including limestone or dolostone enclosed metal deposits, cast limestone deposits, black smoker deposits, skarn deposits, clefts in alpine deposits (i.e. these clefts are bound by folded metamorphic rocks), complex pegmatite deposits (i.e. pegmatites which include four or more mineral species including quartz, a mica group species and a feldspar group species) and even with zeolites in the context of a basalt bound cavity and low temperature hydrothermal deposition. This is why fluorite occurs at thousands of different localities all over the world.

Australia has little in the way of localities that produce fine quality fluorite specimens. Most Australian fluorite localities are located in Tasmania. Tasmanian mines that have produced fine fluorite specimens included Mount Bischoff; The Renison Bell Mine (Renison Mine), North Dundas, near Zeehan and The Mount Cleveland Mine, Luina in the Savage River Regional Reserve. Minor fluorite specimens also occur at Broken Hill, New South Wales as colorless or very pale blue octahedrons a few millimeters on edge on matrixes of manganocalcite and sometimes with alabandite. Pale green fluorite occurs near Mareeba in far northern Queensland.