ANDALUSITE

Andalusite is commonly pink to red, but can be white or even green or gray or other colors. Some andalusite contains the distinctive cross pattern of graphite inclusions (chiastolite). In thin section, andalusite is colorless in plane light and first order colors (typically gray to pale yellow) under crossed polars.

 

Andalusite in hand sample (clicking on some images leads to larger versions)

 

 

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Andalusite (chiastolite) from a graphitic schist, Hamadan, Iran. Andalusite crystals are ~ 1 cm in diameter (Sepahi et al., 2004).

Andalusite-quartz vein from the Nigde Massif, Turkey (Whitney & Dilek, 2001). The large crystal in the middle of the sample is ~ 5 cm long.

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Andalusite in quartz vein, Hamadan, Iran. Hand sample ~ 6 cmin diameter (Sepahi et al., 2004).

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Andalusite from graphitic schist, Hamadan, Iran. Hand sample is ~ 6 cm in diameter.

 

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Andalusite crystal, ~ 2 cm diameter. Photo by S. Kruckenberg

 

 

 

Andalusite-quartz vein, Nigde Massif, Turkey. The andalusite crystals are 1-6 cm long, zoned pink to red (Fe3+ variation), and some crystals are fractured and filled with fibrous sillimanite, which is folded. The quartz veins are boudinaged. Sample diameter (long direction) ~ 20 cm. (Whitney & Dilek, 2001)

 

Andalusite in thin section (clicking on some images leads to larger versions)

 

 

 

Thin section, crossed polars: Andalusite end-section (looking down c-axis), from andalusite-kyanite-sillimanite quartzite, Sivrihisar, Turkey (Whitney, 2002). Andalusite is ~ 3 mm in diameter.

 

 

Thin section, crossed polars: Deformed andalusite (gray, higher relief and coarser grained than quartz) and kyanite (small yellow-gold crystals) in muscovite (green-pink crystals) quartzite,Sivrihisar, Turkey.

 

Thin section, plane light: Andalusite from schist, Hamadan, Iran.

 

 

Thin section, crossed polars: Andalusite (gray) with sillimanite (blue), Hamadan, Iran. Field of view ~ 4 mm.

 

 

Thin section, plane light: Andalusite (pink) with sillimanite (clear), Hamadan, Iran. Field of view ~ 4 mm.

 

Thin section, crossed polars: Same crystal as shown in image above.

 

 

Thin section, plane light: Andalusite end section with opaque inclusions. See Sepahi et al. (2004) for microprobe analysis of this zoned grain. Field of view ~ 4 mm.

Thin section, crossed polars: Same sample as shown in image to the left.

Thin section, crossed polars: Andalusite prism section showing inclusion-rich core region, Hamadan, Iran. Field of view ~ 4 mm.

 

 

 

Thin section, plane light: Andalusite (large crystal, left and center) + fibrous sillimanite (brownish mat to right of andalusite), Hamadan, Iran.

 

 

 

Thin section, crossed polars: Same view as image to left.

 

 

 

 

Thin section, crossed polars: Deformed andalusite from andalusite-fibrolite-quartz vein, Nigde, Turkey. Field of view ~ 4 mm.

 

 

Thin section, plane light: Andalusite in biotite schist, Little Jack terrane, North Cascades, WA (see Baldwin et al., 1997, Tectonics).

 

 

 

Thin section, plane light: Andalusite 'fish' (center), just above image to left, in biotite schist, North Cascades, WA.

 

 

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Thin section, plane light: Asymmetric andalusite from biotite schist, North Cascades, WA. From Baldwin et al. (1997).