Lithiophilite is a mineral containing the element lithium. It is lithium manganese(II) phosphate with formula: LiMnPO4. It occurs in pegmatites often associated with triphylite to which it is closely related. Triphylite being virtually the same mineral except that iron(II) substitutes for manganese giving it the formula LiFePO4. Lithiophylite and triphylite form a solid solution series, a mineral with intermediate composition is known as sicklerite (Li(Mn,Fe)PO4).
Lithiophylite is a resinous reddish to yellowish brown mineral crystallizing in the orthorhombic system often as slender prisms. The Mohs hardness is 4.5 and the specific gravity is 3.35.
It is usually associated with lepidolite, beryl, quartz, albite, amblygonite, and spodumene of pegmatitic origin. It rather readily weathers to a variety of secondary manganese phosphates and oxides. The type locality is Fairfield County, Connecticut where it was first reported in 1878.