Downsite

Where it forms, where it's found

Type locality: Freedom No. 2 Mine
Marysvale Mining District
Piute County
Utah
USA
38.4984°, -112.2143°

1recorded occurrences

Source · OpenStreetMap

Crystallography

Crystal system: Monoclinic
Space group: C2/m
Cell parameters: a = 17.0556(5) Å · b = 10.7947(3) Å · c = 8.8570(2) Å
Cell angles: β = 112.124(3) °
Ratio a:b:c: 1 : 0.633 : 0.519

Chemical composition

Constituent elements: Mass composition breakdown
Element Atoms At. mass g/mol Mass g/mol Mass share
42MoMolybdenum Molybdenum 3 95.950 287.850
42.44%
8OOxygen Oxygen 17 15.999 271.983
40.11%
19KPotassium Potassium 2 39.098 78.196
11.53%
16SSulfur Sulfur 1 32.060 32.060
4.73%
1HHydrogen Hydrogen 8 1.008 8.064
1.19%
Total 678.153 100.00%
Mass share = atoms × atomic mass ÷ molar mass × 100
From IMA formula

Mass composition breakdown
Element	Atoms	At. mass g/mol	Mass g/mol	Mass share
42MoMolybdenum	Molybdenum	3	95.950	287.850	42.44%
8OOxygen	Oxygen	17	15.999	271.983	40.11%
19KPotassium	Potassium	2	39.098	78.196	11.53%
16SSulfur	Sulfur	1	32.060	32.060	4.73%
1HHydrogen	Hydrogen	8	1.008	8.064	1.19%
	Total	678.153	100.00%

Synonyms

Downsiet
IMA2022-119

In other languages

German: Downsit

Classification

Strunz

10th ed.

7.DE

7SulfatesClass
7.DSulfates (selenates, etc.) with additional anions, with H₂ODivision
7.DEWith only medium-sized cations; unclassifiedGroup
7.DEDownsiteSpecies

Literature, links & citation

Citations

2023Bosi, Ferdinando, Hatert, Frédéric, Pasero, Marco, Mills, Stuart J. (2023) Newsletter 72. Mineralogical Magazine, 87 (3) 512-518 doi:10.1180/mgm.2023.21DOI: 10.1180/mgm.2023.21

Cite this entry

@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Downsite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/downsite-470687},
  note      = {Accessed 2026-05-11}
}