1) Trigonal mineral 
Bystrite is a silicate mineral with the formula (Na,K)7Ca(Si6Al6)O24S4.5•(H2O), and a member of the cancrinite mineral group. It is a hexagonal crystal, with a 3m point group. The mineral may have been named after the Malaya Bystraya deposits in Russia, where it was found. Bystrite is a cancrinite mineral and exhibits similar physical properties...