Step into the scientific world of gemstone identification with this fascinating collection of historical gemological articles, carefully curated from early 20th-century and earlier sources for today's readers. Focusing on one of the most essential physical tests in gemology, specific gravity measurement, the volume explains the classic methods used to determine a gemstone's density relative to water, illustrating how this property can help distinguish between different gem materials and support broader gemstone testing. Contents include: Gem Testing by B. W. Anderson Gemstones by G. F. Herbert A Text Book of Mineralogy by Edward Salisbury Dana Gems and Gem Material by Edward Henry Kraus Practical Gemmology by Robert Webster Gem Stones and Their Distinctive Characters by G. F. Herbert Smith With original texts and expert context preserved in an accessible modern edition, this book is a valuable and engaging reference for gem enthusiasts, students, collectors and anyone curious about the foundational techniques of gemstone testing and identification.