Mica Visible Spectra (generally 350 - 2500 nm)

polarizations: (a = alpha direction; b = beta direction; g = gamma direction)

Images of representative mica spectra

Micas usually owe their color to Fe, Mn, Ti, and Cr. Iron contributes as Fe²⁺, Fe³⁺, Fe²⁺ - Fe³⁺ intervalence charge transfer, and as Fe²⁺ - Ti⁴⁺ intervalence charge transfer. Manganese contributes weakly through Mn²⁺, and strongly through Mn³⁺ and associated color centers induced through natural radiation damage. Chromium in the 3+ oxidation state contributes an intense green color to some micas.

Manganese-containing micas

• pink lepidolite spectrum image; Lepidolite, GRR 678, Himalaya Mine, San Diego County, California, 1.0 mm thick with Mn³⁺ in octahedral sites dominating the spectrum. Data Files: a ; g 
• brownish-pink lepidolite spectrum image; Lepidolite, Coolgardie, Western Australia, 1.661 mm thick with Mn³⁺ in octahedral sites dominating the spectrum. Data File: cleavage 
• reddish-purple muscovite spectrum image; Muscovite, GRR 727, Minas Gerais, Brazil, alurgite variety, 0.5 mm thick with Mn³⁺ in octahedral sites dominating the spectrum. Data Files: a ; b ; g 
• pink muscovite spectrum image; Muscovite, GRR 805, Harding Mine, New Mexico, USA, 2.0 mm thick. Data Files: a ; b ; g 
• orange-brown phlogopite spectrum image; Phlogopite, GRR 728, Langban, Sweden, manganophyllite variety, 0.1 mm thick. Data Files: a ; g 

  Iron-containing micas

• medium-green phlogopite spectrum image; Phlogopite, GRR 1575, Ontario, Canada, 1.897 mm thick, showing the Fe²⁺ - Fe³⁺ intervalence charge transfer neae 700 nm, the  Fe²⁺ absorption near 900 nm, and the OH overtone near 940 nm. Data Files: perpendicular to cleavage plane, 24K; parallel to the cleavage plane
• red-brown phlogopite spectrum image; Phlogopite, KB5-2, Kimberley, South Africa, with reverse pleochroism from Fe³⁺ in the tetrahderal site, 0.03 mm thick. Reference: Farmer and Boettcher (1981) Amer. Mineral 66, 1154-1163. Reverse pleochroism means that the most intense absorption occurs when the electric vector of the incident polarized light is parallel to the c-axis, opposite to the case for most common micas. Data Files: a ; b
  
• mica spectrum, Beebe Hole Mine, Tule Mountain, San Diego County, California, 2.66 mm thick cleavage. Polarized perpendicular to the cleavage slab showing the Fe²⁺ bands.
  

• Chromium-containing micas

• green muscovite spectrum image; Muscovite, GRR 1461, near Randsburg, Kern County, California, 0.493 mm thick, showing typical Cr³⁺ absorption near 600 nm. Data Files: cleavage plane
•     another slab, 0.180 mm thick cleavage slab, unpolarized.  Data File
• brown roscoelite spectrum image; Roscoelite, GRR 1927, Stuckslager Mine, Coloma, El Dorado County, California, 0.040 mm thick, showing Cr³⁺ absorption near 600 nm. Data Files: cleavage plane

  Data Files

  • no other data files at this time

Link to an extensive collection of references to mostly color and visible spectroscopy of micas

 Back to the Index of Data Files