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The Strangest Rock: Acude Jerimum, Ceara, Brazil



Roberto Weinberg and Cae Araujo,
School of Geosciences, Monash University, Australia
and Universidade de Sao Paulo, Brazil






This page documents a strange metamorphic rock that crops out in the Acude Jerimum. The rock is comprised of kyanite (upto 5cm long), bronze-coloured sillimanite in radial aggregates (upto 15cm in diameter), garnet (upto 2cm in diameter) and biotite. There are patches of fine-grained garnetite, patches 50cm wide of almost pure silimanite, and red garnet with a thin outer greenish grey rim in regions with biotite and kyanite.


Santa Quiteria granite
Santa Quiteria granite
a) Coarse garnet-biotite-hyanite-sillimnanite rock. b) Zoom in in (a) showing zoned garnet in biotite-kyanite (sillimanite) coarse matrix.
migmatite migmatite
c) d)
e) Coarse kyanite in amongst bronze-coloured sillimanite at contact with biotite-kyanite rocks. Note patches of fine-grained garnetite (the more homogeneous, finer patches). f) Detail of (e).
radial sillimanite radial sillimanite
g) Radial sillimanite, bronze-coloured, 15cm in diameter. h) Radial sillimanite, bronze-coloured, 15cm in diameter..