Borate sulfates

Sturmanite is a rare sulfate mineral with the chemical formula Ca6Fe3+2(SO4)2.5(B(OH)4)(OH)12 · 25 H2O. It crystallises in the tetragonal system and it has a Moh's hardness of 2.5. Sturmanite has a bright yellow to amber colour and falls in the ettringite group. It was named after Bozidar Darko Sturman (born 1937), Croatian-Canadian mineralogist and Curator Emeritus of Mineralogy, Royal Ontario Museum.

Charlesite is a sulfate mineral of the ettringite group. Charlesite was named in 1945 after Dr. Charles Palache, a mineralogist and professor at Harvard University for his work on minerals. This mineral is extremely rare, and when it is found it is usually in crystal (but not gem) form. Its crystals are soft and hexagonal, and can vary in color. Colors can range from clear to white, or even pale yellow or pink. The brittle mineral's Mohs hardness is 2.5 with a specific gravity of 1.79. Though transparent to the eye, the mineral has a white streak.

Fontarnauite is a relatively recently described, rare sulfate, borate mineral with the chemical formula . It is found in an evaporite boron deposit. It coexists with other evaporite boron minerals, especially probertite. It is monoclinic, crystallizing in the space group P21/c.