Figure 4. Many of the crystals show signs of twinning, in which two halves of the crystal are mis-aligned, but joined in the middle. The twins can be recognized by the way light reflects from only one of the twins at a time. This rock is composed of several other minerals, including dark pyroxenes (augite and clinopyroxene) and amphiboles (hornblende and actinolite) (King and Foord, 1994; West and others, 2000).
Last updated on October 6, 2005