Help|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportAdd Glossary Item
StatisticsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

IMA 2010-012 = coralloite

Posted by Marco E. Ciriotti  
avatar IMA 2010-012 = coralloite
March 27, 2012 06:00AM
▪ Callegari, A.M., Boiocchi, M., Ciriotti, M.E., Balestra, C. (2012): Coralloite, Mn2+Mn3+2(AsO4)2(OH)2•4H2O, a new mixed valence Mn hydrate arsenate: Crystal structure and relationships with bermanite and whitmoreite mineral groups. American Mineralogist, 97, 727-734.

Coralloite is a new mineral found at the Monte Nero Mine (Rocchetta Vara, La Spezia, Liguria, Italy) having the simplified formula Mn2+Mn23+(AsO4)2(OH)2·4H2O. It occurs as sub-millimetric lamellar cinnabar-red crystals elongated on <100> and flattened on (001), isolated or forming wisps up to 0.5–1 mm long. Associated phases are calcite, inesite, quartz, brandtite, sarkinite, and tilasite in a chert matrix.
Crystals are pleochroic, yellow along <100> and orange-red in directions normal to it. Extinction is parallel to the cleavage traces and elongation is negative. The small crystal size does not allow accurate determination of refraction indices. Crossed polar observations of crystals placed in diiodomethane (n = 1.74) suggest that the mean refractive index is close to that value.
Coralloite is triclinic, space group P1, a = 5.5828(7), b = 9.7660(13), c = 5.5455(7) Å, α = 94.467(3), β = 111.348(2), γ = 93.850(2)°, V = 279.26(6) Å3, Z = 1. The five strongest lines in the simulated powder diffraction pattern (dobs, I, hkl) are: 9.710 Å, 100.0, (01-0), 5.166 Å, 77.1, (100); 5.136 Å, 79.7, (001); 3.342 Å, 64.8, (1-2-1); 3.324 Å, 33.6, (12-1-).
The structure of coralloite (final Rall 0.044 for 3092 observed reflections) shows similarities with bermanite: Mn2+Mn23+(PO4)2(OH)2·4H2O and ercitite: Na2Mn23+(PO4)2(OH)2·4H2O. In particular, these three minerals exhibit the same structural slab formed by <<6>Mn23+(<4>XO4)2(OH)2>; X = As or P. However, these structural slabs are connected by interposed layers of different polyhedra for each mineral species.

Your Email:


  • Valid attachments: jpg, jpeg, gif, png, pdf
  • No file can be larger than 1000 KB
  • 3 more file(s) can be attached to this message

Spam prevention:
Please, enter the code that you see below in the input field. This is for blocking bots that try to post this form automatically. If the code is hard to read, then just try to guess it right. If you enter the wrong code, a new image is created and you get another chance to enter it right.

Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © and the Hudson Institute of Mineralogy 1993-2015, except where stated. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: October 8, 2015 21:14:46