Romanèchite
Current inventory: 0 gems
 

  
Romanèchite is named after its discovery locality, Romanèche, Saône-et-Loir, France.

Discovered in 1910; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Ba,H₂O)₂Mn₅O₁₀

Hydrated Barium Manganese Oxide

Molecular Weight:

544.25 gm

Composition:

Barium

17.66 %

Ba

19.72 %

BaO

Manganese

48.45 %

Mn

69.62 %

Mn₂O₃

Silicon

0.52 %

Si

1.10 %

SiO₂

Hydrogen

0.44 %

H

3.97 %

H₂O

Oxygen

34.92 %

O

100.00 %

94.41 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.09-30

Nickel-Strunz 10th Ed. ID:

4.DK.10

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
K : With large (+- medium-sized) cations; tunnel structures

Related to:

None

Varieties:

Skemmatite

Synonyms:

Hydrobraunite, Psilomelane (incorrectly)

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Euhedral crystals very rare, flat, ridged, to 200 μm; acicular to fibrous, divergent; commonly reniform, botryoidal, stalactitic, colloform banded; very fine-grained massive. 

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

Irregular/uneven

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0; Vickers: VHN₁₀₀=514-715 kg/mm²

Density:

4.70 - 4.74 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Iron-black, dark steel-gray; gray-white in reflected light

Transparency:

Opaque

Luster:

Sub-metallic, dull when massive

Refractive Index:

R1–R2: (400) 26.7–38.7, (420) 26.3–37.7, (440) 25.6–35.9, (460) 25.2–34.8, (480) 24.8–34.0, (500) 24.3–33.0, (520) 23.8–32.1, (540) 23.4–31.1, (560) 22.9–30.1, (580) 22.4–29.3, (600) 22.0–28.6, (620) 21.6–28.0, (640) 21.3–27.5, (660) 21.2–27.2, (680) 20.9–26.8, (700) 20.7–26.5

Biaxial

Birefringence:

None

Dispersion:

None

Pleochroism:

None

Anisotropism:

Strong. Bireflectance: Strong; gray to white.

Occurances

Geological Setting:

A product of weathering of manganese-bearing oxides, carbonates, silicates; in sedimentary deposits; as replacement deposits in limestones and dolostones; a principal component of “psilomelane” and “desert varnish” (manganese oxide-rich coatings formed on rocks in arid regions); in some plume agates.

Common Associations:

Pyrolusite, Hausmannite, Chalcophanite, Braunite, Goethite, Calcite, Quartz

Common Impurities:

Ba, H, Mn, O

Type Locality:

Manganese deposit, Romanèche-Thorens, La Chapelle-de-Guinchay, Saône-et-Loire, Burgundy, France

Year Discovered:

1910

View mineral photos:

Romanèchite Mineral Photos and Locations

Unusual Gem Categories

Black Gems, Metallic Gems

More Information

Mindat.org
Webmineral.com

Romanèchite is a barium manganese oxide mineral. It is the primary constituent of Psilomelane, which is a mixture of minerals. Romanèchite is commonly found associated with Pyrolusite and other manganese oxide minerals as well as Goethite, Calcite and Quartz. Romanèchite is a valuable ore of manganese, which is essential ingredient in steel and other alloys. It is opaque, black to dark steel-gray with sub-metallic luster and a Moh's hardness of 5 - 6. Romanèchite specimens of black, lustrous, botryoidal masses can be quite attractive. Faceted Romanèchite gems are rare and unusual.

Romanèchite distribution: although common in occurrence, characterization by X-ray, chemical analysis, or both, is necessary. Authenticated from: Romanèche, Saône-et-Loire, France. In Germany, well-crystallized from Schneeberg, Saxony, and at the Clara Mine, near Oberwolfach, Black Forest. From the Restormel mine, Lostwithiel, Cornwall, England. In the USA, at Austinville, Wyeth County, Virginia; from Sodaville, Mineral County, Nevada; at the Hoggett mines, Hidalgo County, New Mexico; at the Tolbard mine, Paymaster district, Imperial County, California. In the Talmantes mine, near Parral, Chihuahua, Mexico. From Pilbara, Western Australia.
 

  
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