PYROAURITE

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 sjögrenite 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

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

Images


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.