Fillowite Locality: Sullivan Mine, Sullivan, New Hampshire Size: miniature, 4.8 x 3.9 x 1.5 cm Fillowite An exceptionally rich example of a very rare manganese phosphate, that I personally had never even seen. However, I am told by those who know more than I do, that this is a very impressive piece, the best seen on the market certainly and better than a few major private holdings have (one source told me , after thinking about museum holdings he had seen, this may be the richest specimen known). The crystallization is both rich and frankly aesthetic, all things considered. It is on the front and the back. From what research I could do, the locality seems to have not yet been publicly reported to produce this species, although with the old Smithsonian label, I would tend to believe it. Its hard to make this stuff up....and there would have simply been no motive at the time. Exchanged from the Smithsonian to the Academy in the 1920s. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Fillowite
Fillowite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Na₃CaMn²⁺₁₁(PO₄)₉.
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Fillowite structural group.
Key properties: Mohs hardness 4.5; specific gravity 3.43; White streak; Subresinous to greasy luster; optically uniaxial.
IMA symbol Fil, grandfathered status — known before the IMA’s founding, named in 1879.
A primary accessory mineral in a zoned granite pegmatite (Branchville, Connecticut, USA).
It is found associated with Triploidite, fairfieldite, reddingite (Branchville, Connecticut, USA).
In honor of Abijah N. Fillow (1822–1895), Branchville, Connecticut, USA, who early supplied minerals from his quarry at the locality.