The beam has a fairly narrow focus and unlike a traditional blacklight, most of the light produced by the UV Photon is just outside the visible spectrum (370 nm). In full darkness it will cause objects to fluoresce at distances of 20 feet or more. In bright daylight the effectiveness is greatly reduced, but is still usable at about 6-12 inches.
From glittering gemstones to fascinating minerals and fossils, Rock and Gem is an incredible celebration of the Earth's buried treasures. Including specially commissioned photographs of more than 450 illustrious specimens and information-rich text, this book illustrates each stone's unique characteristics and its relationship to humankind through the ages.
A remarkable study of the Earth's rocks, minerals, gems, and fossils, this stunning volume reveals the breath and wonder of these outstanding natural phenomena and the fascinating ways they have been prized and used.
Striking visual profiles present the entire range of rocks and minerals, with key information for accurate identification, and practical advice on how to cut, polish, and display objects, as well as an intriguing look at the many ways they have been used, from basic building blocks to fine decoration.(Softcover | | 360 pages | ISBN 9780756633424 | 2005,2008)
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