Pyroaurite, a magnesium ferric-iron carbonate hydroxide hydrate mineral, was first discovered from Sterling Hill by Paul Desautels (Frondel, 1972). It has not been found at Franklin. Pyroaurite commonly occurs as light yellow to yellowish-brown, hexagonal, platy crystals, up to several mm in width, and tabular. Pyroaurite crystals also occur "sprinkled" and "impaled" on acicular willemite.
The luster of pyroaurite is vitreous to dull. No physical or optical data exist. A number of small crystals have been examined semiquantitatively by [Dunn] using microchemical and microprobe methods and were found to be Mg- and Fe3+- bearing, with less than 2 wt. % MnO or ZnO.
Pyroaurite is an uncommon mineral locally, occurring on altered vein surfaces, and is associated with willemite, franklinite, calcite, hodgkinsonite, hetaerolite, and other species. In the north orebody, it was found coating hematite and associated with serpentine and calcite. Dunn and Leavens (1981) reported an occurrence on the 1300 level; these specimens 'consist of willemite-franklinite ore, with chlorophoenicite, sphalerite, barite, willemite and epitactic sjögrenite as secondary minerals. (Dunn, 1995)

 Location Found: Ogdensburg
 Mineral Note: Pyroaurite, var. pyroaurite-3R (pyroaurite), changed to just pyroaurite in Franklin Mineral list in 2017. The mineral sj√∂grenite was recognised as a polytype of pyroaurite and accordingly discredited as a species.
 Year Discovered: 1865
 Formula: Mg6Fe23+(OH)16[CO3] · 4H2O
 Essential Elements: Carbon, Hydrogen, Iron, Magnesium, Oxygen
 All Elements in Formula: Carbon, Hydrogen, Iron, Magnesium, 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   Pyroaurite

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.623. 'Pyroaurite'

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.72

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 23, No. 1 - Spring 1982, pg. 13Mineral Notes Research Reports, Sjögrenite on Pyroaurite
View IssueV. 19, No. 2 - September 1978, pg. 6Recent Mineral Occurrences at Sterling Hill by Stephen Sanford - Pyroaurite (small article)
View IssueV. 8, No. 2 - August 1967, pg. 5Mineralogical Data - Pyroaurite
View IssueV. 7, No. 2 - August 1966, pg. 12The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Pyroaurite (small article)
View IssueV. 7, No. 1 - February 1966, pg. 8Pyroaurite

Hexagonal pyroaurite crystals, calcite, hematite and franklinite from Sterling Hill Mine, Ogdensburg, NJ
Hexagonal pyroaurite crystals (light yellow), calcite (white, tan), hematite (maroon) and franklinite (black) from Sterling Hill Mine, Ogdensburg, NJ. Field of view 3/4" x 5/8". From the collection of, and photo by Robert A. Boymistruk.

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