Graftonite is an iron(II), manganese, calcium phosphate mineral with formula: (Fe2+, Mn, Ca)3(PO4)2. It is a mineral consisting of an iron manganese-calcium phosphate occurring in salmon-pink laminated intergrowths with triphylite. It is a monoclinic-prismatic mineral containing calcium, iron, manganese, oxygen, and phosphorus.
It was first described from its type locality of Melvin Mountain in the town of Grafton, in Grafton County, New Hampshire.
- Category: Phosphate minerals
- Formula: (Fe2+, Mn, Ca)3(PO4)2
- Crystal system: Monoclinic
- Crystal class: Prismatic (2/m) (same H-M symbol)
It forms lamellar to granular translucent brown to red-brown to pink monoclinic prismatic crystals. It has a vitreous luster with a Mohs hardness of 5 and a specific gravity of 3.67 to 3.7.
- Luster: Sub-Vitreous, Resinous, Greasy
- Transparency: Translucent
- Colour: Usually reddish brown, occasionally light brown, rarely salmon-pink
- Comment: Maybe dark brown due to alteration.
- Streak: White to faintly pink, when unaltered.
- Hardness: 5 on the Mohs scale
- Tenacity: Brittle
- Fracture: Irregular/Uneven, Sub-Conchoidal
- Density: 3.67 – 3.79 g/cm3 (Measured) and 3.95 g/cm3 (Calculated)