This is a platy mineral on calcite/andradite/pyroxene/wollastonite rock from Franklin, collected by Roy Epting, Sr. circa 1930s-1950s. It does not fluoresce (it looks dark red from a little bit of underlying calcite color coming through), appears to have one or more very god cleavages and a carefully measured hardness of 5.5. My first thought was barite, but no fluorescence, and have never seen it in plates this large, or wollastonite, but that mineral is in there already as separate yellow-fluorescing grains. So, getting to the rarities, possibly barylite or barysilite, but they have hardnesses of 7 and 3, respectively. Barylite has weak blue fluorescence (with today's lamps), which I have photographed at Harvard, so that leaves barysilite, which has none. Dont have much experience with these, so throwing it out to the Franklin collecting community for help. 7 x 6 x 4.5 cm 265g
Fritz; I think you are going to find that this is bustamite -- possibly ferrobustamite! I'm very interested in any test results, I have been planning to write this assemblage up for the Picking Table. Found with "third find" wollastonite specimens, about 30% of the specimens I have handled. And it does in fact fluoresce a very dark, weak red. JVF
My initial impression was that it does have a very weak red fluorescence, but with the calcite glow as a backdrop I was uncertain. I would never have pegged bustamite as a potential identification, and after reading Dunn I still would not (he makes no mention of a ferrobustamite, either). If it is bustamite then it is an under-reported occurrence. Only piece we found in the collection like this, though in hindsight you might find more. And it would be nice to know I can measure hardness properly cuz bustamite's is reported here on mindat as H=5.5-6.5. A bit has gone out for SEM-EDS analysis.