Publication Type:

Journal Article

Authors:

Kampf, Anthony R.; Mills, Stuart J.; Merlino, Stefano; Pasero, Marco; McDonald, Andrew M.; Wray, William B.; Hindman, James R.

Source:

American MineralogistAmerican Mineralogist, Mineralogical Society of America, Washington, DC, United States, Volume 97, Number 11-12, p.2007-2015 (2012)

ISBN:

0003-004X

Keywords:

Beaver County Utah, Carbonates, cell dimensions, chain silicates, coexisting minerals, crystal chemistry, crystal structure, electron probe data, formula, lattice parameters, nesosilicates, new minerals, orthosilicates, polyhedra, Raman spectra, silicates, space groups, spectra, sulfates, TGA data, thaumasite, tobermorite, United States, utah, x-ray diffraction data

Abstract:

The new mineral whelanite, Cu (sub 2) Ca (sub 6) [Si (sub 6) O (sub 17) (OH)](CO (sub 3) )(OH) (sub 3) (H (sub 2) O) (sub 2) , was approved by the Commission on New Minerals and Mineral Names (IMA) in 1977, but until now a description has not been published. The mineral is orthorhombic with space group Pn2n and cell parameters a=5.6551(4), b=3.683(3), c=27.1372(7) Aa, V=565.3(5) Aa (super 3) , and Z=1. The mineral occurs with thaumasite, stringhamite, and kinoite in a copper-rich, diopside-garnet-magnetite skarn at the Bawana mine, Beaver County, Utah, and has also been confirmed to occur at other localities. At the Bawana mine, it is found as irregular clusters and radial aggregates of platy to lath-like crystals up to 1 mm in length, flattened on {001} and elongated on [100]. The color and streak are pale blue and the luster is vitreous. The laths are flexible, but not elastic. Cleavage is perfect on {001} and good on {010}, producing splintery fracture. The Mohs' hardness is about 2 and 1/2. The measured density is 2.74(3) g/cm (super 3) and the calculated density is 2.737 g/cm (super 3) based upon the empirical formula. The mineral is biaxial (-), alpha =1.612(2), beta =1.622(calc), and gamma =1.626(2), and 2V (sub meas) =64(1) degrees . The pleochroism is weak: X=Y (pale blue) 4sigma F) contains two different types of polyhedral layers parallel to {001}, which alternate along [001] and are linked to one another by sharing corners with wollastonite-like silicate chains running parallel [010]. One polyhedral layer, consisting of edge-sharing CaO (sub 7) polyhedra, is identical to that in the structures of the tobermorites (tobermorite 9Aa, tobermorite 11Aa, tobermorite 14Aa, and clinotobermorite). The other layer is brucite-like, with alternating ribbons of edge-sharing Cu (super 2+) O (sub 6) and CaO (sub 6) octahedra. Disordered CO (sub 3) and H (sub 2) O groups are also located in the interlayer region. The crystal structure of whelanite exhibits OD character.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2013-004030<br/>Bawana Mine<br/>kinoite<br/>stringhamite<br/>whelanite