Autunite Group.
Unstable at room temperature and dehydrates fairly rapidly to metaheinrichite (Walenta, 1965) which may be fully transparent. Most of the specimens shown on the photos here are probably metaheinrichite.
History
Activities related to discovery and approval of the group members
Structural context
Heinrichite
Crystal System monoclinicCrystal Class prismaticSpace Group P2/c