Guides
Long-form guides on gemmological method: what origin determination can show, which factors decide quality and value, and how gemmology began.
Pages in this section
- Origin determination and its limitsOrigin determination compares a specimen's measurable features with reference databases for known localities and yields a probabilistic "consistent with" conclusion; it is not an intrinsic property of a material, and for small strung beads it is usually neither economical nor reliable.
- Quality grading and value factorsThe "4Cs" apply to diamonds and cannot be transferred to coloured stones; apart from a few materials such as diamonds, coloured diamonds and pearls, most coloured stones have no common grading scale — only descriptive trade terms.
- How gemmology became a technical disciplineGemmology became a technical discipline only in the 20th century — from the loupe and refractometer to spectroscopy, X-ray imaging and trace-element analysis. What can be measured decides what can be known.