gems, gemology,

Gübelin and Schmidt discuss apparent discrepancies encountered when comparing numerical data and descriptive statements in gemological textbooks, explaining how apparently conflicting values can arise from differences in specimens, measuring techniques, instruments, environmental conditions, terminology, and the degree of precision with which gemological constants are reported. The paper is intended to show that variations between authoritative texts need not represent actual errors, but may reflect the natural variability of gem materials and differences in the circumstances under which observations were made.