I've been meaning to do this for a long time. Below is a fine specimen of banded tourmaline. Tourmalines like this are generated in pegmatites; see diagram below the picture, with description and link to more information. (The diagram is not from the same place as the description.) The Pegmatite Zone, from whence cometh this text: "A pegmatite is a coarse grained igneous rock (formed deep within the earth) having a grain size of 3cm or more. Mostly pegmatites are granitic in origin, that is they are composed of granite and its constituents like quartz, feldspar and mica. In addition...
