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Coquimbite
Current inventory:  0 gems
 

  
Coquimbite is named for the province of Coquimbo, Chile where it was discovered.

Discovered in 1841.   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Fe³⁺₂(SO₄)₃•9(H₂O)

Hydrated Iron Sulfate

Molecular Weight:

562.02 gm

Composition:

Iron

19.87 %

Fe

28.41 %

Fe₂O₃

Hydrogen

3.23 %

H

28.85 %

H₂O

Sulfur

17.12 %

S

42.74 %

SO₃

Oxygen

59.78 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Sulfates

Strunz 8th Ed. ID:

6/C.08-40

Nickel-Strunz 10th Ed. ID:

7.CB.55

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H₂O
B : With only medium-sized cations

Related to:

Dimorph of Paracoquimbite.

Varieties:

Aluminous Coquimbite

Synonyms:

Blakeite (of Dana)

Crystal Data

Crystallography:

Trigonal - Hexagonal Scalenohedral

Crystal Habit:

As short prismatic to pyramidal crystals, dominated by {1010}, {1120}, {1011}, {0001}, to 2 cm; massive, granular.

Twinning:

None

Physical Properties

Cleavage:

Imperfect on {1011}; difficult on {1010}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

2.5

Density:

2.11 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Soluble in cold water; soluble in acids, astringent taste; efforesces in dry air as a white powder.

Optical Properties

Color:

Pale Violet to Amethystine, rarely pale Yellow or pale Green

Transparency:

Translucent to Transparent

Luster:

Vitreous

Refractive Index:

1.360 - 1.572  Uniaxial ( + )

Birefringence:

0.0070

Dispersion:

Low

Pleochroism:

None

Occurances

Geological Setting:

Typically a secondary mineral in the oxidized portions of weathering iron sulfide deposits in arid regions; rarely associated with fumarolic activity.

Common Associations:

Copiapite, Paracoquimbite, Voltaite, Szomolnokite, Römerite.

Common Impurities:

Al

Type Locality:

Coquimbo Region, Chile

Year Discovered:

1841

View mineral photos:

Coquimbite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Coquimbite is a rare iron sulfate mineral. Mineral specimens can be very attractive with colors of bright violet to Amethyst purple. Faceted gems are extremely rare and very small due to crystal sizes. Coquimbite is very difficult to facet because it is very soft (2.5) and soluble in water. Facetable crystals were almost non-existant until a recent find at the Javier Mine, Ayacucho Departmen, Peru.

Coquimbite is found in only a few locations including Alcaparrosa Mine, Cerritos Bayos, Calama, El Loa Province, Antofagasta Region, Chile; Copiapó Province, Atacama Region, Chile; Faraglione Nico, Porto Levante, Vulcano Island, Eolie Islands, Lipari, Messina Province, Sicily, Italy; Javier Mine, Ayacucho Department, Peru; Rio Tinto Mines, Minas de Riotinto, Huelva, Andalusia, Spain; and San Rafael District, Emery County, Utah, USA.
 

  
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