Freeform step-cut whewellite, 3.12 cts, 15.6 x 6.8 mm, Czech Republic. © The Gem Trader. Used with permission.
Seldom seen even in mineral collections, whewellite is very rarely faceted. It’s mostly desired as a curiosity because of its scarcity, chemical composition, and unusual — sometimes organic — origins.
| Data | Value |
|---|---|
| Name | Whewellite |
| Crystallography | Monoclinic. Crystals prismatic or equant, also in twins. |
| Refractive Index | 1.489-1.651 |
| Colors | Colorless, white, yellowish, brownish. |
| Luster | Vitreous to pearly. |
| Hardness | 2.5-3 |
| Fracture | Conchoidal |
| Specific Gravity | 2.19-2.25 |
| Birefringence | 0.159-0.163 |
| Cleavage | Good in 1 direction. 2 others distinct |
| Dispersion | 0.034 |
| Luminescence | None. |
| Luminescence Present | No |
| Transparency | Transparent to translucent. |
| Absorption Spectrum | Not diagnostic. |
| Formula | CaC2O4 · H2O (calcium oxalate). |
| Pleochroism | None. |
| Optics | α = 1.489; β = 1.553; γ = 1.649-1.651. Biaxial (+), 2V= 80°. |
| Optic Sign | Biaxial + |
| Etymology | After William Whewell, English natural scientist and philosopher. |
| Occurrence | Coarse crystals occur in coal seams and concretions (organic origin). Also as a hydrothermal mineral in ore veins. |
Whewellites, 0.8 x 0.6 x 0.2 cm, Burgk, Dresden, Saxony, Germany. © Rob Lavinsky, www.iRocks.com. Used with permission.
A rare mineral, whewellite can develop both in the Earth and through organic means. It can grow hydrothermally in carbonate-sulfide veins and can also occur in coal seams as well as in concretions in plants and animals, most notably as kidney stones.
Although whewellites have fairly high dispersion, any faceted gems would be too small to appreciate this property. They have variable cleavage (from good to fair) in three directions and an extremely low hardness (a copper coin could scratch them). Thus, cutting and wearing them as jewelry stones is difficult.
Whewellites are best treated as display pieces for gem or mineral collections.
Whewellite, source unknown, from the collection of the Lille Natural History Museum, Lille, France. Photo by Vassil. Public Domain.
Scientists have synthesized whewellites for numerous projects, such as research into kidney stone formation and crystal twinning. However, there is no known jewelry use for this lab-created material.
None known.
Notable mineral sources include the following:
Whewellite crystal, from the collection of the National Museum, Prague, Czech Republic. Photo by Sbisolo. Licensed under CC By-SA 3.0.
Crystals are usually very small and colorless. From these, faceters could cut gems that typically weigh about 2 carats.
Avoid cleaning whewellites with any solution that contains acids. Clean only with warm water, mild detergent, and a soft brush.
Whewellites contain oxalates (C2O4), and their consumption can lead to kidney stone formation. While these are present in some common foods and pose a risk if ingested over time, whewellites contain oxalates in greater concentration. Faceters should wear dust masks to avoid accidentally ingesting particles.
Exposure to whewellite dust may also cause acute skin irritation, especially in children and pets, so faceters should wear protective clothing and make sure to clean their workspace. A glovebox to contain dust would be ideal.
For more safety tips, see our article on lapidary health hazards.
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