Melanterite
Current inventory:  0 gems
 

  
Melanterite was named in 1850 from the Greek copperas, meaning ferrous sulfate or black metallic dye.

Discovered in 1850;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Fe²⁺(SO₄)•7(H₂O)

Hydrated Iron Sulfate

Molecular Weight:

278.02 gm

Composition:

Iron

20.09 %

Fe

25.84 %

FeO

Hydrogen

5.08 %

H

45.36 %

H₂O

Sulfur

11.53 %

S

28.80 %

SO₃

Oxygen

63.30 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Sulfates

Strunz 8th Ed. ID:

6/C.06-10

Nickel-Strunz 10th Ed. ID:

7.CB.35

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

Related to:

Melanterite Group. Iron analogue of Chalcanthite.

Varieties:

Cuprian Melanterite, Cuprokirovite, Kirovite, Manganoan Melanterite, Mg-bearing Melanterite, Zincian Melanterite

Synonyms:

Copperas, Green Vitriol, Iron Vitriol, Melantherite, Sulphate of Iron

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals are rare, equant, pseudo-octahedral, to short prismatic [001], showing {120}, {001}, may be thick tabular {010}, {102}, many smaller modifying forms, to 20 cm; commonly stalactitic, in concretions and crusts, massive, pulverulent, and as efflorescences.

Twinning:

None

Physical Properties

Cleavage:

On {001}, perfect; on {120}, distinct

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

2.0

Density:

1.895 - 1.898 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Soluble in water. May dehydrate to the mineral Siderotile.

Health Warning:

CAUTION: Poisonous! May contain sulfuric acid. Do not lick or ingest. Do not touch with bare hands or wash hands immediately after handling!

Optical Properties

Color:

Green, pale Green, Greenish Blue, Bluish Green, Colorless; Colorless to pale Green in transmitted light.

Transparency:

Transparent to Translucent, Opaque

Luster:

Vitreous

Refractive Index:

1.470 - 1.486  Biaxial  ( + )

Birefringence:

0.0150 - 0.0160

Dispersion:

None to Weak; inclined, r > v

Pleochroism:

None

Occurances

Geological Setting:

A secondary mineral formed by the oxidation of iron sulfide minerals, such as pyrite and marcasite, it is found occurring naturally in sheltered crevices and cavities in sulfidic sedimentary and metamorphic rocks, and in coal and lignite deposits. It also forms readily on the walls, timbers, and other structures in mines.

Common Associations:

Pisanite, Chalcanthite, Epsomite, Pickeringite, Halotrichite, other sulfates.

Common Impurities:

Cu, Mg

Type Locality:

n/a

Year Discovered:

1850

View mineral photos:

Melanterite Mineral Photos and Locations

More Information

Mindat.org 
Webmineral.com

Melanterite is one of only a few water soluble sulfate minerals. It is the iron analog of Chalcanthite. Melanterite is a hydrated iron sulphate mineral formed after the decomposition of pyrite or other iron minerals due to the action of surface waters. It is often found in mines as a post-mining formation on mine walls as encrustations or stalactites. It is subject to dehydration and may dehydrate to the mineral Siderotile. Some specimens my have a beautiful blue-green color and may be fairly transparent. Faceted gems are very rare and are extremely difficult to cut due to the softness (Mohs 2.0) and water solubility. Gems should be stored in an air tight container since they may be subject to dehydration. Melanterite should be handled with caution because of the possible presence of sulfuric acid.

Melanterite occurs at many localities, a few with large crystals. In Germany, from the Rammelsberg mine, near Goslar, Harz Mountains. At Falun, Sweden. From Rio Tinto, Huelva Province, Spain. At Idria, Slovenia. Large crystals on the island of Cyprus. From Cantiere Conche, Elba, Italy. At Baia Sprie (Felsóbánya), Romania. From Damar, Murgul, northeast Anatolia, Turkey. In the USA, at the Alma mine, Leona Heights, Alameda County, and the Island Mountain mine, Trinity County, California; from Ducktown, Polk County, Tennessee; at Butte, Silver Bow County, Montana; in the Lucky Boy mine, Bingham district, Salt Lake County, Utah. At volcanoes on the Kamchatka Peninsula, Russia. From Tierra Amarilla, southeast of Copiapó, Atacama, Chile.
 

  
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