AM_Tweddillite Formula: Ca Sr Al1.43 Mn1.313 Fe.257 Si3 O13 H Name: Tweddillite Unit cell: 8.934 5.718 10.325 90.0 114.54 90.0 , V=479.80 Space group: P121/M1 (11)

Armbruster T , Gnos E , Dixon R , Gutzmer J , Hejny C , Dobelin N , Medenbach O , Mineralogical Magazine , 66 (2002) p.137-150, Manganvesuvianite and tweddillite, two new Mn3+-silicate minerals, from the Kalahari manganese fields, South Africa, Locality: Kalahari manganese fields, South Africa