Assess an antique gemstone through its documentation and physical condition. Identity, treatment, condition, setting and provenance answer different questions, so record them separately.
Begin with identity
Confirm whether the material is natural, laboratory-grown or a simulant. Early synthetics and later replacements are common enough that every important stone deserves attention.
Treatment changes care
Coloured stones may be heated, filled, oiled, dyed, coated or diffusion-treated. Ask what was detected and whether heat, solvents, steam or ultrasonic cleaning could cause trouble.
Origin is a laboratory opinion
For eligible stones, a report may offer an opinion on geographic origin based on inclusions, properties and comparison samples. Inconclusive results happen. Research the mounting date and former owners through dated records and construction evidence.
Inspect colour in context
View the stone face-up and from the side in more than one light. Note zoning, extinction, windowing, transparency and the mounting. Foil, closed backs and darkened metal can change the apparent colour considerably.
Record condition before cleaning
Look for chips, abrasions, surface-reaching fractures, loose stones and old repairs. Cleaning that is harmless to diamond may damage treated emerald, opal, pearl or another sensitive material.
Keep provenance on paper
Invoices, auction catalogues, dated photographs, wills and signed family records can support ownership history.
Make the invoice useful
Record the gemstone, stated origin, detectable treatments, report number, mounting, known repairs and return terms. Historically important claims should travel with their supporting documents.
GIA's guide to gem treatments explains disclosure and care. Its coloured-stone report guide separates identification, treatment and geographic-origin opinions.