Microscope Image in Crossed Polarized Light of a Mauritian Trachyte (image) University of the Witwatersrand Share Print E-Mail Caption Variably sized crystals of alkali feldspar like the large white one at lower left are aligned by magmatic flow. A large zircon crystal appears as the brightly coloured grain just right of centre. Credit Wits University Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.