Mineral Macro No. 42-27859970
by Bernardo Cesare - © Corbis. All Rights Reserved. - © Bernardo Cesare/Visuals Unlimited/Corbis
Thin section of a granulite from Antarctica
26 Mar 2010 --- Thin section of a granulite from Antarctica. Intergrowths between crystals may be regular and characterized by abundant crystal faces or chaotic and full of strange shapes. In this image, the orange-brown biotite and the blue worm-like quartz grew simultaneously in a symplectic intergrowth that is believed to indicate low nucleation and growth rates in the replacement of a preexisting mineral during metamorphism. This metamorphic sample is unusual because it went to ultra-high-temperature of over 900 8C, very rarely recorded about 550 million years ago. During the slow cooling, the biotite-quartz intergrowth replaced a former crystal of garnet. Polarized, LM --- Image by © Bernardo Cesare/Visuals Unlimited/Corbis
