Mineral
Ludlamita
Fe₂(PO₄)₂·4H₂O · Fosfatos
Uncommon on the market. Ludlamite forms in phosphate-rich hydrothermal environments. Its deep green colour, vitreous lustre and prismatic habit make it much valued. It can be confused with vivianite, but it is more stable. Much Brazilian ludlamite occurs on rather unattractive rocky and sandy matrices, though with well-formed crystals.
Etymology
Named in honour of Thomas L. Ludlam, a 19th-century American collector.