Scheelite
A tungsten-bearing mineral, commonly sought after for its blue fluorescence under a blacklight.
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Description
Scheelite - chemical formula CaWO4 is a tungsten-calcium mineral that is a primary ore for tungsten (chemical element “W”). The mineral bears its name for the Swedish chemist Carl Wilhelm Scheele who gathered tungstic acid from scheelite in 1781.
Scheelite is a popular piece among rockhounds, who often seek out this mineral with a blacklight (UV light). Glowing blue under UV light, the mineral becomes arguably more brilliant than its regular white, brown, yellow, orange, or green.
Crystals of pure scheelite are considered rare and more commonly found within muscovite - a sheeted, silicate mineral.
Scheelite crystals form tetragonal structures that often resemble dipyramids (two pyramids conjoined at their bases), but can also form tubular, columnar, or grainy aggregates.
Occurrence
In the United States, scheelite has been mined primarily in North Carolina, California, and Nevada. Throughout the world, other scheelite producers are Bolivia, New Zealand, Russia (Siberia), Switzerland, Australia, Brazil, and France. However, perhaps the best pieces of scheelite are mined in Mt. Xuebaoding, China, producing some of the best scheelite specimens in the world.
Scheelite often forms in compact groups within hydrothermal veins in granite, gneiss, and pegmatite - an igneous rock that forms at the last stage of magma crystallization, bearing large and coarse crystals.
Many other minerals are often found within scheelite-bearing formations including fluorite, wolframite, molybdenite, and gold due to the hydrothermal origin of many scheelite deposits.
Rock Hounding
Probably the most exciting way to rockhound is a night with a blacklight. Anyone who has been rock hounding spends most of a day or afternoon in an adult sandbox with a shovel, and maybe a sieve - for those of you more advanced. Though it may be enjoyable, it is often difficult to distinguish between particular minerals in regular daylight or find interesting pieces at all.
Scheelite, and other various fluorescent minerals, glow under a blacklight and are much more obvious to find in the open.
Rock hounds can search for common locations for scheelite deposits within surrounding areas and may be lucky enough to have some nearby.
Mine test pits through granitic veins may be good locations to find such occurrences of scheelite, though due diligence searching beforehand before just heading out with a blacklight!
Test pits or debris piles that may have scheelite, are likely to not have any high-quality ore deposits but are great locations for collecting interesting pieces. Most anything found under a blacklight on your own will likely have little to monetary value, but having a rock in your collection that glows under UV light is definitely a piece worth keeping to show off.
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References
Ridgley, V. (2018). Scheelite – Mineral properties, photos and occurrence. https://mineralexpert.org/article/scheelite-mineral-tungsten-ore
The Editors of Encyclopaedia Britannica. (1998, July 20). Scheelite | Tungsten, ore, mining. Encyclopedia Britannica. https://www.britannica.com/science/scheelite
Nice, thanks. Here's my take on an example that's not large visible crystals, but interesting in UV light. https://richardigibson.substack.com/p/starry-starry-night