Cianciulliite



Cianciulliite is a manganese magnesium zinc hydroxide hydrate mineral. The composition of the type material, recalculated as described by Dunn et al. (1991), is MnO 29.7, MgO 9.86, ZnO 33.36, H2O 27.08, total = 100.0 wt. %, with two molecules of water per 5 divalent cations, recalculated by difference.
Cianciulliite was first described from Franklin by Dunn et al. (1991). It has not been reported from Sterling Hill.
The crystal structure of cianciulliite has a brucite-type layer of Mg and Mn octahedra with tetrahedrally coordinated Zn atoms capping the octahedral holes. The apical (OH) of Zn tetrahedra are hydrogen-bonded to the water layer. Some of the water is readily lost in experimentation (Grice and Dunn, 1991).
Cianciulliite occurs as small (0.6 mm) euhedral crystals with highly lustrous faces, some of which are curved. The crystals are slightly tabular on and the pinacoid is dull to pearly; this differential luster is the most distinctive physical feature of this mineral. Incipient perfect cleavages are abundant, adding to this anomalous luster. Cianciulliite is dark reddish brown in transmitted light, but crystals appear dark brown to black in hand specimen. The mineral is very soft, and the density, calculated for 2 water molecules per 5 divalent cations, is 2.87 g/cm3.
Optically, cianciulliite is biaxial with undetermined sign; the indices of refraction are between 1.76 and 1.92 and were calculated to be 1.79 - 1.80 for sodium light. In reflected light, cianciulliite is weakly anisotropic, gray, weakly bireflectant, and not observably pleochroic. In oil, the color in reflected light is a slightly darker and bluer gray; internal reflections are orange-red and clearly evident. Reflectance measurements and color values were given by Dunn et al. (1991). There is no discernible fluorescence in ultraviolet.
Cianciulliite is known on but one small museum specimen from the Franklin Mine. The matrix is a mixture of willemite and zincite which has replaced crystals of an unknown species. An irregular coating of presumed Mn-oxides is followed by a final crystallization of cahnite and cianciulliite. To date, cianciulliite is a rare mineral. (Dunn, 1995)


 Location Found: Franklin (Type Locality), unique to Franklin/Ogdensburg area
     
 
 Year Discovered: 1991
     
 Formula: Mn(Mg,Mn)2Zn2(OH)10 · 2-4H2O
 Essential Elements: Hydrogen, Magnesium, Manganese, Oxygen, Zinc
 All Elements in Formula: Hydrogen, Magnesium, Manganese, Oxygen, Zinc
     
 IMA Status: Approved
     
     
 To find out more about this mineral at minDat's website, follow this link   Cianciulliite

     
 References:
Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.588


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 36, No. 1 - Spring 1995, pg. 12Closest-Packing and Hydrogen Bonds in Minerals of the Franklin Marble, Paul B. Moore - Cianciulliite
View IssueV. 33, No. 2 - Fall 1992, pg. 30New-to-the-Science: Cianciulliite (Description)
View IssueV. 32, No. 2 - Fall 1991, pg. 3Notes from the Laboratory & Changes to the List of Species From Franklin and Sterling Hill, Pete J. Dunn, John L. Baum, Cianciulliite
     
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