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Mineral F (of Dunn)


Mineral F (of Dunn)

Rare Mineral

Description Tabs

Sterling Mine, Ogdensburg, Sussex County, New Jersey, United States of America
Size Range: 
Small miniature (3-4.5 cm)
2.5 × 3.3 × 2.5 cm

Mineral F (of Dunn) is an unnamed  mineral “officially” known as UM1986-10-CO:ClHMgMnZn. This specimen is from the analyzed find. (See “Analysis” tab).

Until recently, the Mindat species page for UM1986-10-CO:ClHMgMnZn stated that that it was unnamed but valid. It now states that it is “probably invalid”. But according to Pete Dunn (the original investigator), “It is assuredly a new mineral species; only its definition is unclear.” (“Franklin and Sterling Hill, New Jersey: the world’s most magnificent mineral deposits”, p. 689.)

Will it, or can it, ever be “defined” (according to current IMA standards)? I don’t know, but, as far as I can tell, mineralogists are not beating down the doors to get samples for whatever work needs to be done. Nonetheless, it is an interesting “thing”. Perhaps, as has been the case for several “UKs” from MSH (e.g. MSH UK 60 = arisite-(Ce)), it will eventually be found elsewhere in a form that permits complete characterization. Presumably the Sterling Mine would then be a co-type locality.

In the first pair of photos (FOV 6.9 x 4.5 mm), Mineral F consists of “frothy”, pearly, looking cream colored spheroids. This is the “classic” appearance of this “mineral”. The largest spheroid is 2.2 mm. The rhombs in the center are a non-fizzy carbonate.

The matrix is ordinary franklinite ore in calcite. As can be seen from the SW UV photo, there is also a bit of willemite, mostly as a “rind” surrounding themineral F cavity. The franklinite crystals are small and somewhat rounded. Most of the exposed ones are broken. The calcite fluoresces the usual bright orange-red. (But this isn’t meant to be a fluorescent display specimen.)

Single item shipping weight (small box) is 2.9 oz. Up to a total weight of 8 oz (225 g), this could be combined with other items from this or future auctions for the same postage. If you wish to keep an “open box”, let me know. 

Mineral Data
What's on the rock

Mineral F (of Dunn)

Synonym Of: 


Mg5(Zn,Mn)3(CO3)2(OH,Cl)12 · H2O
Mg5(Zn,Mn)3(CO3)2(OH,Cl)12 · H2O
Analysis Report - only: Mineral F (of Dunn)
LMB minerals

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In addition to the standard terms and conditions, please note the following. Almost all IDs are visual. While in most cases the ID is obvious, there may be cases where it is not. If you are doubtful about a particular ID, please ask for more information. Or do not bid! Similarly, if you are not sure that the specimen meets your criteria, do not bid. I have tdone the best I can with the photos. Nevertheless, if you are not happy with a specimen for any reason, I will refund the bid price – but not the shipping costs (unless the fault is clearly mine) – if the specimen is returned. This policy applies even if analysis of the specimen shows that my ID was incorrect. When in doubt, ask - or don’t bid. Note that most crystals at MSH and Varennes are micros - even if on large specimens. Please pay attention to the stated sizes. Any customs duties, fees etc. are the responsibility of the buyer.