Optical Spectra of Sodalite, Na₄(Si₃Al₃)O₁₂Cl 

• Ballentyne DWG, Bye KL (1970) The nature of photochromism in chlorosodalites from optical data. Journal of Physics D: Applied Physics 3, 1438-1443.
• Belichenko VP, Mazykin VV, Platonov AN, Tarashchan AN (1973) Paramagnetic sulfur radicals in dark-colored hackmanites and natural lazurites. Dopovidi Akademii Nauk Ukrains'koi RSR, Seriya B:  Geologiya, Geofizika, Khimiya ta Biologiya 35, 99-101. In Ukrainian
• Chang IF (1974) Synthesis of photochromic and cathodochromic sodalite. Journal of the Electrocheical Society 121, 815-820.
• Annerstein H, Hassib A (1979) Blue sodalite. Canadian Mineralogist 17,  39–46.
• Scarratt K (1986) Notes from the The Laboratory. Journal of Gemmology 20, 35-39.
• Arieli D, Vaughan DEW, Goldfarb D (2004). New Synthesis and Insight into the Structure of Blue Ultramarine Pigments. Journal of the American Chemical Society, 126, 5776–5788. https://doi.org/10.1021/ja0320121
• Ravikumar RVSSN, Chandrasekhar AV,Yamauchi J, Reddy UP, Rao PS (2005)  Tetrahedral site of iron in natural mineral sodalite. Radiation Effects & Defects in Solids 160, 109–115.
• Kondo D, Beaton D (2009) Hackmanite/sodalite from Myanmar and Afghanistan. Gems & Gemology 45, 38-43.
• Williams ER, Simmonds A, Armstrong JA, Weller MT (2010) Compositional and structural control of tenebrescence. Journal of Mater. Chemistry, 20, 10883–10887. 
• Finch AA, Friis H, Maghrabi M (2016) Defects in sodalite‑group minerals determined from X‑ray‑induced luminescence. Physics and Chemistry of Minerals 43, 481-491.  
• Blumentritt F, Fritsch E, Caldes MT, Jobic S (2019) Introduction to mineralomimetism: the case of photochromic sodalite hackmanite. 36th International Gemmological Conference IGC, August 2019, Nantes, France, p75-77.
• Blumentritt F, Fritsch E (2021) Photochromism and Photochromic Gems: A Review and Some New Data (Part 1). The Journal of Gemmology 37,780-800.
• Yan XX, Yue SW, Su LM, Wang ZW (2021) White Sodalite with Tenebrescence. Spectroscopy and Spectral Analysis 41, 3936-3941 (in Chinese)
• Bumentritt F, Notari F, Caplan C (2024) Properties and Colouration of Orange Hackmanite from Afghanistan. The Journal of Gemmology, 39, 160–170.
  

Optical Spectra of Tugtupite, Na₄BeAlSi₄O₁₂Cl

• Povarennykh AS, Platonov AN, Tarashchan AN, Belichenko VP (1971) Color and luminescence of tugtupite (beryllosodalite) from Ilimaussaq, South Greenland. Meddelelser om Groenland 181, 1-12.
• Blumentritt F, Fritsch E (2021) Photochromism and Photochromic Gems: A Review and Some New Data (Part 1). The Journal of Gemmology 37, 780-800.

Optical Spectra of Lazurite

• Chukanov NV, Sapozhnikov AN, Shendrik RY, Yigasina ME, Steudel R (2020) Spectroscopic and Crystal-Chemical Features of Sodalite-Group Minerals from Gem Lazurite Deposits. Minerals  10, 1042. https://doi.org/10.3390/min10111042
  
• Farsang S, Caracas R, Adachi TBM, Schnyder C, Zajack Z (2023) S₂^– and S₃^– radicals and the S₄^2– polysulfide ion in lazurite, haüyne, and synthetic ultramarine blue revealed by resonance Raman spectroscopy. American Mineralogis 108, 2234-2243.
  

Optical Spectra of Lapis Lazuli, (lazurite, haüyne, sodalite)

• Schwarz KH, Hofman U (1970)    Z. Anorg. Allg. Chem. 378, 152-
• Faye GH (1971) A Semi-quantitative Microscope Technique for Measuring the Optical Absorption Spectra of Mineral and Other Powders. The Canadian Mineralogist 10, 889-895.
• Seel F (1984) Sulfur in Artwork: Lapis Lazuli and Ultramarine Pigments. Studies in Inorganic Chemistry 5, 67-89.
• Scarratt K (1986) Notes from the The Laboratory. Journal of Gemmology 20, 35-39.
• Banerjee A (1993) Correlation between Colour and Fluorescence of Lapis lazuli. Z. Naturforsch. 48a, 1267-1268.
• Reinen D, Linder GG (1999) The nature of the chalcogen colour centres in ultramarine-type solids. Chemical Society Reviews 28, 75-84.

Optical Spectra of Haüyne

• Kiefert L, Hänni HA (2000) Gem-quality haüyne from the Eifel District, Germany. Gems & Gemology, 36, 246–253.  https://doi.org/10.5741/gems.36.3.246.
  
• Kondo DM, Laurs BM, Fritz E (2008) Gem News International: Gem-quality afghanite and haüyne from Afghanistan. Gems & Gemology 44, 79–80.
  
• Srisataporn B (2024) Greem Haüyne, A Rarity among Sodalite Gems. The Journal of Gemmology 39, 13-16