Prices per carat
Sourced auction results, stone by stone
Lab reports and treatments
Heat, oil, glass and origin
Gemstones A to Z
What each stone is
Comparisons
Look-alike stones, side by side
Free, sourced guides to colored gemstone prices, lab reports and treatments.
Guides
Nov 8, 2026
•
1 min read
Ruby vs. sapphire, spinel vs. ruby, Colombian vs. Zambian emerald and more: how to tell them apart and how they are priced.
Ruby, sapphire, emerald, spinel, tourmaline, alexandrite, tanzanite and garnet: what each stone is and how it is priced.
Lab Reports
+1
Heat, oil, glass and origin: every Carat Brief guide to the lab language that moves a gemstone's price.
Price Guides
2 min read
Every Carat Brief price guide in one place, built on named auction results and producer disclosures.
Garnet
+2
4 min read
Two greens, two minerals: price, rarity, durability and treatment, compared.
Emerald
3 min read
Color, clarity, treatment and what the public Gemfields auction prices show about Zambian emerald.
Tanzanite
One source, often heated: tanzanite's color, durability and what public auction results show per carat.
Auctions
What Sotheby's is offering on November 11, what the lab reports say, and what the estimate means per carat.
Nov 7, 2026
The facts from each lab's own pages, and where a shared phrase like pigeon blood can hide different criteria.
Where each lab lets you check a report, what you need, and what a match does not prove.
The real wording behind minor oil, and how to tell it apart from no oil.
+3
What labs mean by NTE, TE and the residue codes, and what the phrase does not promise.
Named sales from about $4,500 to $116,152 per carat, and how color change and origin read on a report.
What emeralds have sold for, from under $5,000 to about $305,000 per carat, and why the gap is so wide.
Every recent Montepuez ruby and Kagem emerald sale in one place, from Gemfields' own announcements.
Nov 6, 2026
What large tanzanite has sold for, and what GIA says drives its value.
Tourmaline
What Paraíba tourmaline has sold for, and why a price per carat can mislead.
5 min read
What sapphires sell for by size, treatment and origin, with a named source for every figure.
Nov 4, 2026
The price gap, how labs tell the difference, and when the premium is worth paying.
Ruby
6 min read
Color, origin, treatment, and why two red stones can be worth $5 or $1 million a carat.
The auction records, the price per carat, and the three attributes every record-setter shares.
How to spot it, why it isn't really ruby, and what it's actually worth.
Spinel
Nov 3, 2026
How to tell them apart, why spinel was mistaken for ruby for centuries, and why it still costs a fraction.
7 min read
What a ruby is actually worth by quality, origin, treatment and size, and how to read the numbers.
Alexandrite
Aug 20, 2026
8 min read
What GIA and SSEF publish about alexandrite's color change, what each hue says about origin and quality, and what the auction record shows.
