Silicate Minerals - Cyclosilicates

Cyclosilicates

Cyclosilicates (from Greek κύκλος kuklos, circle), or ring silicates, have linked tetrahedra with (T_xO_3x)2x- or a ratio of 1:3. These exist as 3-member (T₃O₉)6- and 6-member (T₆O₁₈)12- rings, where T stands for a tetrahedrally coordinated cation. Nickel-Strunz classification: 09.C

• 3-member ring
  • Benitoite - BaTi(Si₃O₉)
• 6-member ring
  • Axinite - (Ca,Fe,Mn)₃Al₂(BO₃)(Si₄O₁₂)(OH)
  • Beryl/Emerald - Be₃Al₂(Si₆O₁₈)
  • Cordierite - (Mg,Fe)₂Al₃(Si₅AlO₁₈)
  • Tourmaline - (Na,Ca)(Al,Li,Mg)_3-(Al,Fe,Mn)₆(Si₆O₁₈(BO₃)₃(OH)₄

Note that the ring in axinite contains two B and four Si tetrahedra and is highly distorted compared to the other 6-member ring cyclosilicates.

• Cyclosilicate, - 6-membered single rings, beryl (red: Si, blue: O)

• Cyclosilicate, - 3-membered single ring, benitoite

• Cyclosilicate, - 4-membered single ring, papagoite

• Cyclosilicate, - 9-membered ring, eudialyte

• Cyclosilicate, - 6-membered double ring, milarite