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.