The Four Cs, read carefully.

Color

For colored stones, color is everything. It accounts for roughly 50–70% of the value, depending on the species. What color and where on the spectrum? Saturation (intensity), hue (the pure color direction — blue vs. teal vs. violet-blue), and tone (how light or dark).

A 3-carat ruby with medium saturation is worth less than a 1.5-carat ruby with high saturation — even if the smaller stone has worse clarity. Color outranks carat by a wide margin.

Locality matters — sometimes decisively

For certain species, the country of origin adds a premium because buyers associate specific localities with specific colors. Kashmir sapphires command a premium for their velvety blue. Burmese (Mogok) rubies for "pigeon blood" red. Colombian emeralds (Muzo, Chivor) for a slightly bluish-green. Paraíba tourmalines for neon copper-blue. These are not snobbery — they reflect genuine chromatic and inclusion-profile differences.

Cut

For colored stones, cut is evaluated on two axes: (a) how well the cut shows the color (a poorly-cut sapphire can look dark; a well-cut one can look electric), and (b) proportion — is the stone cut symmetrically? Are the facets meeting cleanly?

A well-cut stone in the 1–3 carat range will outperform a poorly-cut 5-carat stone on almost every metric buyers actually care about.

Clarity

Clarity on colored stones is graded from VVS1 (near-perfect) down through VVS2, VS1, VS2, SI1, SI2, to included. For many species — emeralds especially — perfect clarity is extremely rare and not always desired; some inclusions ("gardens" in emerald, silk in sapphire) are diagnostic of locality and add character.

For diamonds, the clarity scale matters more: the difference between VVS2 and VS1 can be a 15% price difference, even if neither is visible to the eye.

Carat

Carat is simply weight — one carat is 0.2 grams. Two stones of the same carat can be dramatically different in apparent size depending on their cut and species (a 1-carat emerald looks larger than a 1-carat diamond because emerald is less dense).

Carat matters, but it matters least of the four. A small, exquisitely coloured Kashmir sapphire is worth more than a large, dull one — and significantly more than a large, oversaturated Madagascan sapphire of the same carat.

The two that matter most

If you remember nothing else: color first, cut second. Everything else arranges itself around those two.