Zircon is common as an accessory mineral in a variety of igneous and metamorphic rocks, and as a detrital heavy mineral in clastic sedimentary rocks. Its very high positive relief relative to quartz and feldspars is evident in A, in which euhedral to subhedral prismatic zircons are enclosed by quartz and feldspar.  Zircon is uniaxial and has parallel extinction in elongate grains.  Interference colours range to third and fourth order, evident in B and D.  In C and D, numerous small anhedral zircons are enclosed in green amphibole.  The dark rims around the zircons are known as pleochroic halos.  A and B are from the Somesville Granite, Acadia, Maine and C and D are from the Tunk Lake Pluton, Maine.  All views are 2.2 mm across.  A, C ppl, B, D x-nicols.