Cerrussite
For centuries every decent Roman matron would paint her face with a cream containing White Lead in order to give the impression that she never saw the sun, since a decent Roman wife was expected to have ‘stayed at home and span wool’ as many gravestones put it. As well as its millennia of cosmetic use this lead carbonate forms amazing lattices of cyclically twinned crystals (known as reticular, or knee shaped) such as the 2 cm specimen in the photo.