- The primary unit is a double ring, with a formula of Si 12 O 30.
- Frankamenite belongs to the triclinic crystal system, with the bases of its structure containing Ca-Na mixed octahedra joined by octagonal tubes SiO 4 of the composition ( Si 12 O 30 ).
- Electrical switching in chalcogenide semiconductors emerged in the 1960s, when the amorphous chalcogenide Te 48 As 30 Si 12 Ge 10 was found to exhibit sharp, reversible transitions in electrical resistance above a threshold voltage.
- Brewsterite-Sr, the more common of these, is a hydrous strontium and aluminium silicate, ( Sr, Ba ) 2 Al 4 Si 12 O 32 ?0H 2 O . Small amounts of barium is usually present replacing part of the strontium.
- "' Frankamenite "'is the fluorine-dominate variation of the rare mineral canasite with a general formula of K 3 Na 3 Ca 5 ( Si 12 O 30 ) [ F, ( OH ) ] 4 ?( H 2 O ).