Optical Spectra of Astrophyllite, K₂NaFe²⁺₇Ti₂(Si₄O₁₂)₂O₂(OH)₄F

• Manning PG (1969a) On the origin of colour and pleochroism of astrophyllite and brown clintonite. Canadian Mineral 9, 663-677
  

• Perekalina ZB, Khomyakov AP (1999)  Diffuse reflection spectra of some titanosilicate minerals. Kristallografiya 44, 139-142. In Russian.