Kyanite

Typically blue in hand sample with bladed crystals.

In thin section: colorless, commonly twinned, high-relief, cleavages prominent.

Below are photomicrographs (plane light and crossed polars) and other images of kyanite. Click on an image to see a larger version. The fields of view are 2-4 mm in each photomicrograph.

Thin section, plane light; Kyanite in Raft River quartzite, Utah (sample from R. Gottardi & C. Teyssier)

Thin section, crossed polars; Kyanite in Raft River quartzite, Utah (sample from R. Gottardi & C. Teyssier)

Thin section, crossed polars: Kyanite in muscovite schist from the Solitude Range, British Columbia (Whitney & Ghent, 1993)

Thin section, plane light: Kyanite in biotite schist, Mica Creek, British Columbia. Thin section, crossed polars: Kyanite in biotite schist, Mica Creek, British Columbia.

Thin section, crossed polars: Kyanite inclusions in andalusite in a kyanite-andalusite-sillimanite (+ staurolite) quartz vein, Hamadan, Iran (Sepahi et al., 2004).

 Thin section, crossed polars: Kyanite - intergrown and twinned crystals in quartz vein, Hamadan, Iran (Sepahi et al., 2004). Thin section, crossed polars: Deformed/kinked kyanite from a kyanite-garnet-biotite schist, Dutchess County, NY.

Thin section, crossed polars: Kyanite (large grayish crystals, lower half of photo) + sillimanite (brighter colored needles next to kyanite) in a kyanite-sillimanite schist, Hamadan, Iran.

Thin section, plane light: Deformed kyanite in kyanite-garnet-biotite schist, Dutchess County, NY (Whitney et al., 1996a, b). Thin section, plane light: Kyanite + quartz inclusions in garnet in a sillimanite-biotite gneiss. Most of the field of view is garnet, with oriented rutile needles. The prominent diagonal lines are cracks. North Cascades, Washington (Whitney, 1991).
Thin section, plane light: Garnet + kyanite (upper left, with staurolite) + sililmanite (fibrous) + andalusite, from the Santander Massif, Colombia. Sample courtesy of Carlos Alberto Rios. Thin section, crossed polars: Deformed/kinked kyanite, Hamadan, Iran. Thin section, crossed polars: Garnet inclusion (black) in twinned kyanite (yellow and gray adjacent crystals), Dutchess County, NY.
Thin section, plane light: Bent kyanite from kyanite-biotite schist, Mica Creek, British Columbia. Thin section, plane light: Kyanite in kyanite-cordierite-biotite-gedrite gneiss, Thor-Odin dome, British Columbia. Kyanite is surrounded by cordierite, with incipient development of spinel symplectite on lower kyanite crystal. Back-scattered electron image: Kyanite (center, dark gray) partially replaced by staurolite (left side of gray crystal, brighter region), in kyanite-andalusite-sillimanite quartzite, Sivrihisar, Turkey (Whitney, 2002). Field of view = 0.5 mm.