Thadeuite
Thadeuite is an IMA-recognized mineral species in the phosphate class, with the chemical formula CaMg₃(PO₄)₂(OH,F)₂.
It crystallizes in the orthorhombic crystal system (space group C222_1).
Key properties: Mohs hardness 4; specific gravity 3.25; White streak; Vitreous luster; optically biaxial.
IMA symbol Thd, IMA status: approved, named in 1978.
Found as a very rare primary mineral in the margins of hydrothermal veins, formed between 230° –360° C and 100–1000 bars.
It is found associated with Fluorapatite, wolfeite, topaz, muscovite, sphalerite, quartz, chalcopyrite, pyrrhotite, siderite, arsenopyrite, chlorite, vivianite, althausite, panasqueiraite.
The mineral was named to honor Professor Décio Thadeu, Technical University, Lisbon, Portugal, for his studies on Portuguese ore deposits.