Triploidite Locality: Abija N. Fillow Quarry (Branchville Quarry), Branchville , Redding , Fairfield County, Connecticut , USA ( Locality at mindat.org ) Size: 7.0 x 4.8 x 2.6 cm. A rare phosphate, from the type locality circa late 1800s. The triploidite is the radiating, embedded, marginally crystalline reddish material. From the noted collection of William Drown who, according to the Mineralogical Record Archive on him, was an umbrella manufacturer who used his fortune to amass a collection of some 6000 mineral specimens. His collection was kept by his family for a generation after his death and then donated in 1918. Ex. Philadelphia Academy of Sciences Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Triploidite
An uncommon manganese-iron hydroxyphosphate forming slender striated prisms.
Intro adapted from Wikipedia (CC BY-SA).
Triploidite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Mn²⁺₂(PO₄)(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Wagnerite structural group.
Key properties: Mohs hardness 4.5–5; specific gravity 3.7; White, nearly streak; Vitreous, adamantine, greasy luster; refractive index 1.727; optically biaxial.
IMA symbol Tpd, grandfathered status — known before the IMA’s founding, named in 1878.
An uncommon hydrothermal alteration product of primary phosphates in complex zoned granite pegmatites.
It is found associated with Triplite, lithiophilite, triphylite, eosphorite, dickinsonite, rhodochrosite.
The name comes from triplite and the Greek for form, as it closely resembles that species.