Allactite



Allactite is a manganese arsenate hydroxide mineral. Microprobe analyses (Dunn, 1983b) indicate that local material approaches end-member composition with but small amounts of Mg, Fe, and Ca substituting for Mn. Zinc substitution is limited, varying from 1.4 - 3.0 wt. %.
Allactite was first reported from Franklin and Sterling Hill by Palache (1935).
Allactite from both Franklin and Sterling Hill occurs as superb 1-6 mm crystals. At Franklin, in general, they are bladed and tabular; those found at Sterling Hill in 1981 are considerably thicker.
The color varies; most specimens are brown, but the 1981 find at Sterling Hill was of distinctly brownish-red crystals. The luster is vitreous, inclining to adamantine. No physical measurements have been made. The tabular habit is somewhat diagnostic; X-ray methods are best for verification.
The diversity of assemblages evidenced by available specimens suggests that allactite may have been moderately common at Franklin but overlooked; it was reported from the Palmer Shaft by Palache (1935). It occurs primarily in carbonate-bearing vein assemblages and is associated with many minerals, among them pyroaurite, leucophoenicite, adelite, hodgkinsonite, barite, willemite, friedelite, and caryopilite. Franklin allactite crystals, in addition to forming clusters, also form druses on slickensides, some of which are coated with Mn-oxides and form thin crusts and veinlet fillings.
At Sterling Hill, allactite has been recovered in substantial quantities in recent years, but the crystal size is generally smaller than at Franklin, most being less than 2mm. Commonly associated minerals include kraisslite, sarkinite, willemite, rhodochrosite, barite, and calcite; less common associated minerals are fluorite, covellite, chlorophoenicite, friedelite, and secondary copper minerals.
The best of Sterling Hill allactite is that found in 1981 in divergent sprays, 3 mm in approximate size, and formed of thick brownish red crystals (Dunn, 1983b). Allactite has also been found as colorless lath-like microcrystals coating thin vein-sidewall surfaces, as white splotchy patches on black oxidized vein surfaces, and as druses. Notable occurrences have been on the 1200 and 1500 levels. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1884
     
 Formula: Mn72+(AsO4)2(OH)8
 Essential Elements: Arsenic, Hydrogen, Manganese, Oxygen
 All Elements in Formula: Arsenic, Hydrogen, Manganese, Oxygen
     
 IMA Status: Approved
     
     
 To find out more about this mineral at minDat's website, follow this link   Allactite

     
 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.656

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.40


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 25 No. 1 - Spring 1984, pg. 8Mineral Notes Research Reports, Allactite
View IssueV. 24, No. 1 - Spring 1983, pg. 4Recent Mineral Occurrences at Sterling Hill, Stephen B. Sanford, Allactite
View IssueV. 19, No. 2 - September 1978, pg. 6Recent Mineral Occurrences at Sterling Hill by Stephen Sanford - Allactite (small article)
View IssueV. 15, No. 1 - February 1974, pg. 8Mineral Notes - Allactite/McGovernite (small article)
View IssueV. 10, No. 1 - February 1969, pg. 12Additional Mineral Notes - Allactite (Short Note)
     
Images

     
Allactite crystals, fluorite, willemite and minor secondary copper from Sterling Hill Mine, NJ.
Stout allactite crystals in subparallel, slightly radial growth (red), fluorite (white), willemite (pink-tan) and minor secondary copper (green-blue) from Sterling Hill Mine, NJ. Field of view 3/4". From the collection of, and photo by Robert A. Boymistruk.


Allactite crystal on chlorophoenicite, Sterling Hill Mine, Ogdensburg, NJ
Allactite crystal (red-brown) on chlorophoenicite (white) from Sterling Hill Mine, Ogdensburg, NJ. Field of view 4 mm. From the collection of, and photo by DW.







All content including, but not limited to, mineral images, maps, graphics, and text on the Franklin-Ogdensburg Mineralogical Society, Inc. (FOMS) website is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.
Creative Commons License