Carat Brief is a free weekly newsletter on the colored gemstone market, published every Tuesday since May 2026. It covers auction records, origin trends, treatment risks, certification issues and public pricing signals for ruby, sapphire, emerald, spinel, tanzanite, alexandrite, tourmaline and garnet.
Every price we publish comes from a named public source: an auction house's own lot page, a producer's disclosure such as Gemfields' auction announcements, or a named trade guide such as GemGuide as reported by JCK. For what a lab report says, we quote the labs themselves: GIA, SSEF, Gübelin, GRS and AGL.
When we divide a sale price by a stone's weight, we mark the result "our arithmetic". When no reliable public figure exists, we say so instead of estimating. Every guide ends with a Useful Sources list so you can check each number yourself.
We do not value individual stones and we do not give investment advice. A handful of auction results does not establish a price for your stone: a lab report and an independent appraisal do. We publish the public reference points so you can ask better questions before you buy.
The weekly brief is free. Carat Brief Pro adds the full Index, live alerts, a monthly deep dive and the full archive. The free guides on this site stay free.
Colored gemstone prices per carat
Gem lab reports and treatments
Colored gemstones A to Z
Gemstone comparisons
Every past edition
Carat Brief is editorial and is not investment advice.