Brandtite is a calcium manganese arsenate hydrate mineral. A partial analysis by [Dunn] of a specimen from the black-willemite ore shows minimal substitution of Fe or Mg; Zn was not determined. Brandtite from the red-willemite ore has Mn > > Mg and, as shown by Parker and Troy (1982), the arsenates from the red ore are predominantly Mn and Mg rich.
Brandtite was reported from Sterling Hill by Gaines (1959); it has not been found at Franklin.
Brandtite occurs in elongate prismatic crystals; some are lath-like. They are up to 0.3 mm in length and commonly form radiating aggregates, but may occur randomly oriented; clusters up to 12 mm have been found. Brandtite is commonly colorless, but may be light brown or light yellow; it is easily stained. There is no discernible fluorescence in ultraviolet. It can be confused with some chlorophoenicite; X-ray methods are best for verification.
The original 1940 find of Sterling Hill brandtite was between the 1400 and 1500 levels and was in the black-willemite zone "near a point where over-breakage had trespassed slightly into the adjacent brown willemite" (Gaines, 1959). This brandtite was associated with rhodochrosite and chalcopyrite in a matrix of calcite, franklinite, brown willemite, and sphalerite.
Additional occurrences of brandtite in the black-willemite zone have been recorded on the 1480, 1500, and 1600 levels, where it is associated with sphalerite, willemite, barite, loellingite and quartz. Brandtite is also found on the 1400 level in white to light brown sheave-like aggregates with sarkinite on a red-willemite matrix. It also occurs in white acicular sprays, associated with willemite, about 50 feet above the 1000 level, in the east branch of the west limb. (Dunn, 1995)

 Location Found: Ogdensburg
 Year Discovered: 1888
 Formula: Ca2(Mn2+,Mg)(AsO4)2 · 2H2O
 Essential Elements: Arsenic, Calcium, Hydrogen, Manganese, Oxygen
 All Elements in Formula: Arsenic, Calcium, Hydrogen, Magnesium, Manganese, Oxygen
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
 To find out more about this mineral at minDat's website, follow this link   Brandtite

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.659

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.46

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 24, No. 1 - Spring 1983, pg. 5Recent Mineral Occurrences at Sterling Hill, Stephen B. Sanford, Brandtite
View IssueV. 19, No. 2 - September 1978, pg. 7Recent Mineral Occurrences at Sterling Hill by Stephen Sanford - Brandtite (small article)
View IssueV. 18, No. 1 - March 1977, pg. 5Recent Mineral Occurances at Sterling Hill by Stephen Sanford - Sarkinite and Brandtite
View IssueV. 17, No. 1 - March 1976, pg. 5Sterling Hill Minerals - Brandtite
View IssueV. 7, No. 2 - August 1966, pg. 6The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Brandtite (small article)
View IssueV. 1, No. 1 - February 1960, pg. 6Brandite (small article)

Brandtite, franklinite and willemite from Sterling Hill Mine, Ogdensburg, NJ
Brandtite (clear elongate prismatic crystals), franklinite and willemite from Sterling Hill Mine, Ogdensburg, NJ. Field of view 3/4" x 3/4". From the collection of, and photo by Robert A. Boymistruk.

Brandtite on franklinite, Sterling Hill Mine, Ogdensburg, NJ.
Brandtite (clear elongate prismatic crystals) on franklinite from Sterling Hill Mine, Ogdensburg, NJ. Field of view 3 mm. From the collection of, and photo by DW.

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