This report focuses on a selection of some of the most valuable gemstones in the global gem trade; ruby, sapphire, emerald, chrysoberyl, tsavorite garnet, tanzanite, and the gem minerals (topaz, aquamarine, tourmaline) found in pegmatites or rhyolites. Exploration criteria for other gemstones such as opal, nephrite jade, jadeite jade, zircon, lapis lazuli, and rhodonite are beyond the scope of this report.
For each gem mineral covered in this report, background information is introduced and the physical and chemical characteristics are presented. The geology and genesis of each gem deposit type is summarized and exploration guidelines listed. Because pegmatites are so closely associated with several gemstones including aquamarine, tourmaline and topaz, there is a chapter devoted to pegmatites and their gem minerals. Topaz rhyolite is a distinctive deposit type which is discussed in Chapter Eight. Application of the exploration criteria to Yukon geology is given in Chapter Nine. A reference list is provided for those readers who want to pursue further details.