Wattersite is a rare mercury chromate mineral with the formula Hg+14Hg+2Cr+6O6.[1] It occurs in association with native mercury and cinnabar in a hydrothermally altered serpentinite.[2] It was first described from Clear Creek claim, San Benito County, California, USA in 1961.[4] It was named to honor Californian mineral collector Lucius "Lu" Watters.[2]
| Wattersite |
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 Black crystals of wattersite with yellowish zones of edgarbaileyite. Locality: Clear Creek claim (Clear Creek Mine), Picacho Peak, New Idria District, Diablo Range, San Benito Co., California, USA. Dimensions: 6.6 cm x 4.8 cm x 4.1 cm |
| General |
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| Category | Chromate mineral |
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Formula
(repeating unit) | Hg+14Hg+2Cr+6O6 |
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| Strunz classification | 7.FB.15 |
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| Dana classification | 35.4.2.1 |
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| Crystal system | Monoclinic |
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| Crystal class | 2/m |
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| Space group | C2/c (number 15) |
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| Unit cell | 859.81 ų |
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| Identification |
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| Color | Dark red-brown to black |
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| Crystal habit | Prismatic, aggregates, massive |
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| Twinning | [001], contact twins on {100} |
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| Cleavage | None |
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| Fracture | Conchoidal |
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| Tenacity | Brittle |
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| Mohs scale hardness | 4.5 |
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| Luster | Sub-Metallic |
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| Streak | Brick red |
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| Diaphaneity | Opaque |
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| Specific gravity | 8.91 |
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| Optical properties | Biaxial |
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| Refractive index | nα = 2.440 - 2.520 nγ = 2.700 - 2.860 |
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| Birefringence | δ = 0.260 - 0.340 |
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| Pleochroism | Visible |
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| Dispersion | r > v strong |
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| References |
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