The Collaborative International Dictionary
Botryogen \Bot"ry*o*gen\, n. [Gr. ? cluster of grapes + -gen.] (Min.) A hydrous sulphate of iron of a deep red color. It often occurs in botryoidal form.
Wiktionary
n. (context mineral English) A hydrous magnesium sulfate mineral.
Wikipedia
Botryogen is a hydrous magnesium sulfate mineral with formula: MgFe(SO)(OH)ยท7HO. It is also known as quetenite.
It crystallizes in the monoclinic prismatic system and typically occurs as vitreous bright yellow to red botryoidal to reniform masses and radiating crystal prisms. Its specific gravity is 2 to 2.1 and its Mohs hardness is 2.
It occurs in arid climates as a secondary alteration product of pyrite-bearing deposits.
It was first described in 1828 for an occurrence in the Falu mine of Falun, Dalarna, Sweden. It was named for its grape like appearance from Greek botrys for bunch of grapes and genos to bear.