Mosesite
A variety of Minerals
What is Mosesite?
Mosesite is a very rare mineral found in few locations. It is a mercury mineral found as an accessory in deposits of mercury, often in conjunction with limestone. It is known to be found in the U.S. states of Texas and Nevada, and the Mexican states of Guerrero and Querétaro. It was named after Professor Alfred J. Moses (1859–1920) for his contributions to the field of mineralogy in discovering several minerals found alongside mosesite. The mineral itself is various shades of yellow and a high occurrence of spinel twinning. It becomes isotropic when heated to 186 °C (367 °F).
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Key Characteristics
Characteristics of Mosesite
Mosesite is a minute yellow crystal with imperfect cleavage along {111} and uneven fracture. It is brittle with a hardness of 3.5. Long exposure, a month or more, to light will change Mosesite to a light olive green color. The powdered form retains its color streaking a light yellow. The mineral exhibits no pleochroism and displays uneven birefringence in polarized light. Heat has a notable effect on Mosesite for when heated above 186 °C (367 °F) the mineral becomes isotropic. This corresponds optically with the observed crystal form only at this higher temperature. It is considered weakly anisotropic. The index of refraction is n = 2.065±0.01. It has an adamantine luster that officially ranges in color from lemon yellow to canary yellow. Mosesite reacts chemically with HCl leaving a residue of HgCl.
Composition of Mosesite
Mosesite contains 16 Hg, 3 Cl, 1½ SO4, ½ CO3 , ½ MoO4, 16 H, and 8 N with a volume of 8.4777x10 nm³ and calculated density of 7.53 g/cm³. The accepted formula for mosesite is Hg2N(Cl,SO4,MoO4,CO3)•H20.
Quick Facts
Physical Properties
- Color
- Yellow; turns olive-green upon prolonged exposure to light.
- Hardness (Mohs)
- 3 - 4
- Density
- 7.53 g/cm³
- Streak
- Very light yellow
Chemical Properties
- Chemical Formula
- (Hg2N)(Cl,SO4,MoO4) · H2O
- Elements
- Cl, H, Hg, Mo, N, O, S

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