Petedunnite



Petedunnite is a calcium zinc silicate mineral of the pyroxene group and the Zn analogue of diopside, hedenbergite, and johannsenite. Solid solution of these components in petedunnite is extensive; Zn is the dominant cation, and the species was defined on the basis of a plurality of Zn.
Petedunnite is the rarest of the clinopyroxenes from Franklin. It was described by Essene and Peacor (1987). It is not known from Sterling Hill.
Petedunnite is dark green, with poor cleavage, vitreous luster, and a calculated density of 3.35 g/cm3. Crystals are prismatic to equant, dull in luster, and up to 2 cm in size. There is no discernible fluorescence in ultraviolet; it is a very boring mineral.
Petedunnite occurs on very atypical specimens found on the Buckwheat Dump in Franklin by Richard Bostwick. One specimen consists of dark-green petedunnite crystals, surrounded by light green clinopyroxene and associated with willemite, calcite, genthelvite (the first local occurrence of this species), gahnite, albite, quartz, galena, sphalerite, titanite, apatite, allanite, and other species. (Dunn, 1995)

Since Dunn’s first description of petedunnite, large quantities of this mineral have been found on the Taylor Road dump, and the Buckwheat dump. It has been found in some surprising places, such as road fill on Cork Hill Road in Ogdensburg, and in a pile of Franklin minerals collected in the 1960’s and dumped on a farm in upstate New York! Most specimens have a notable feature - the light green phase of petedunnite often features exsolution willemite, appearing as tiny dots and presenting a “mossy” fluorescent pattern.


 Location Found: Franklin (Type Locality)
     
 
 Year Discovered: 1983
     
 Formula: Ca(Zn,Mn2+,Mg,Fe2+)Si2O6
 Essential Elements: Calcium, Oxygen, Silicon, Zinc
 All Elements in Formula: Calcium, Iron, Magnesium, Manganese, Oxygen, Silicon, Zinc
     
 IMA Status: Approved 1983
     
     
 To find out more about this mineral at minDat's website, follow this link   Petedunnite

     
 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.435


The Picking Table References
 PT Issue and PageDescription / Comment
V. 59, No. 2 - Fall 2018, pg. 13Memories of Petedunnite
View IssueV. 47, Combined Issue 2006, pg. 29Observable Genthelvite in the Petedunnite Assemblage From Franklin, NJ. (Paragraph about Petedunnite starts at the bottom of pg. 29)
View IssueV. 28, No. 2 - Fall 1987, pg. 14New To Science Petedunnite (small article)
View IssueV. 28, No. 1 - Spring 1987, pg. 3From the Laboratory, Dr. Pete J. Dunn, John L. Baum, Petedunnite
     
Images

     
Petedunnite, microcline feldspar, quartz, franklinite, Talylor Road Dump Frankln
Petedunnite (green daylight mineral) in microcline feldspar, with quartz and franklinite from Talylor Road Dump, Franklin. Non-fluorescent. Photo by WP.


Petedunnite, willemite, microcline, calcite, hematite and quartz from Buckwheat Dump, Franklin, NJPetedunnite, willemite, microcline, calcite, hematite and quartz from Buckwheat Dump, Franklin, NJ under shortwave UV Light
Petedunnite (light green, dark green), numerous tiny spots of exsolution willemite, microcline (gray), calcite (white), hematite (red) and quartz (clear) from Buckwheat Dump, Franklin, NJ. 8" x 4 3/4". From the collection of, and photo by JVF.
Petedunnite, willemite, microcline, calcite, hematite and quartz from Buckwheat Dump, Franklin, NJ under shortwave UV light. The willemite fluoresces green, calcite orange-red, the petedunnite, microcline, hematite and quartz are non-fluorescent. 8" x 4 3/4". From the collection of, and photo by JVF.







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