Aerinite
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Description
A rare light, blue clay mineral occasionally used as a pigment. Aerinite has been found in Andorran murals dated to 1163 as been recorded from Romanesque frescoes that were found in chapels in the Catalan Pyrenees (Casas and Llopis, 1992). Aerinite has semitransparent prismatic crystals that are birefringent. It is resistant to chemicals, heat, and light although it changes to a green-blue shade when heated over 150 C.
Synonyms and Related Terms
aerinita (Esp.); erinite (It.)
Physical and Chemical Properties
- Color = blue-blue-green
- Crystal habit = fibrous
- Luster = vitreous
- Mohs hardness = 3
- Specific gravity = 2.48
- Streak = bluish white
- Ref. Index = <1.66
Resources and Citations
- A.Casas, J.Llopis "The Identification of Aerinite as a Blue Pigment in the Romanesque Frescoes of the Pyrenean Region" Studies in Conservation, 37:132-136, 1992.
- Mactaggart, P. & Mactaggart, A. (June 2007) ‘Blue Pigments’ In: Pigment ID using Polarised Light Microscopy from: Blue Pigments
- Wikipedia: Aerinite Accessed Feb 2026