All About Willemite – Uses, Properties, Color, and Worth
Willemite is a zinc silicate mineral that can be found as crystals, fibers, or grains. This brittle, yet somewhat hard, mineral is widely known for its ability to fluoresce. Willemite gained its popularity due to its abundance in the Franklin District of New Jersey, USA.
Willemite was given its name by a man named Serve-Dieu Abailard Levy who was granted professorship at the University of Liege by King William I (1772 – 1843) of the Netherlands. Levy had discovered the new zinc silicate and in appreciation of the professorship he received, named it after King William I.
Sphalerite, being a chief mineral of zinc, can undergo an alteration of its ore contents and can become what we know as willemite. Willemite stone will typically be associated with limestone but can also be found in marble due to metamorphism of earlier formations of hemimorphite or smithsonite.
Willemite will often occur with zincite, which is a zinc oxide, and franklinite, which contains a high concentration of iron. In these mixtures, only the willemite will fluoresce.
Willemite is not considered to be a rare mineral. There are a few different variations of willemite that are available that many may not know about such as Beta, Sea Foam, Radial, and Grape willemite.
Additionally there is Troostite containing Maganese, and Xingshaoite which contains a large percentage of Cobalt. Most of these variations can be found in the Franklin and Sterling Hill Mines in New Jersey, USA.
Some do get the pronunciation of willemite incorrect. The correct pronunciation is in similar to saying “will” + “a” + “might”.
Uses of Willemite
For the most part, willemite is used as a specimen of fluorescence. It had uses in the past as an ore for zinc and also at one point in time it was used in early television tubes for its brilliant green fluorescence.
Artificial willemite was originally used in the beginnings of the fluorescent tube until further technological advancements replaced it. Now, for the most part, you can find willemite in many rock collector’s holdings, especially those that collect the fluorescence rocks.
Willemite crystals are rare and will at times be used as jewelry. Due to the fragility of willemite, these crystals are not often cut for this purpose. These crystals will also not appear to spectacular when faceted until it is put under UV light.
Some Common Willemite Properties:
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| Willemite Mohs Hardness Scale: | 5.5 |
| Specific Gravity: | 3.9 – 4.2 |
| Streak: | Colorless to White |
| Fracture: | Uneven |
| Willemite Luster: | Vitreous, Resinous |
| Crystal System: | Trigonal |
| Willemite Chemical Formula: | Zn2SiO4 |
What is the color of Willemite?
The color of willemite can be colorless, gray, red, dark brown, yellow, green, and blue. The more common known color of willemite will be its bright fluorescence of green. Willemite is also known to fluoresce in colors of yellow-greens and very rare occasions of slightly blue.
One of the beautiful occurrences of willemite is when it occurs with an amount of calcite in the mix. The combination of the fluorescent green with the fluorescent red/orange while under UV light is quite interesting to visually behold.
Some specimens of willemite are phosphorescent, which means it can luminesce for a period of time after being exposed to the radiation of a UV light. Some specimens have been reported to luminesce for over an hour after UV exposure.
Some other notable minerals found in collectors collections that can fluoresce are the very popular calcite and fluorite.
The Worth of Willemite
Willemite price can get a bit on the expensive side for larger and very colorful fluorescing specimens. Expect to pay anywhere from $20 to well over $100 for a half pound rock. The price will quickly increase with size and in many cases when other fluorescing minerals also exist in the rock.
Tsumeb, Namibia crystal specimens can cost you upwards of a few hundred USD. Quality willemite gemstones that have been cut into some of the larger sizes have ended up in places like the Smithsonian Institution and the Harvard Mineralogical Museum which holds a whopping 36.93 carat specimen.
It is possible to obtain willemite jewelry. Willemite stone can be cut and polished and attached to necklaces, earrings, and rings. Most of this jewelry can be quite affordable until you start getting into cut crystals. Willemite crystals, as I have mentioned, can be quite rare and will easily run you up into hundreds of US dollars.
Other smaller and more common specimens of willemite can range in the $30 USD or below. Though these may be cheaper they still hold a lot of beauty in their fluorescence.
Where can Willemite be found?
Willemite can be found in the following locations; Africa, Canada, Greenland and in Arizona and New Jersey of the United States.
