Ruby Buying Guide: Natural vs Lab-Grown, Prices per Carat & Quality

What is ruby?

Ruby is red corundum (aluminium oxide coloured by chromium) — the same mineral as sapphire. Hardness: 9 on the Mohs scale.

Colour and quality factors

Colour drives most of the value: a pure, saturated red with slight blue is ideal, often called 'pigeon's blood' (a trade term some labs use only for specific criteria). Too dark, brownish or pinkish reduces value. Silk inclusions are normal; transparency and brightness matter.

Origins and natural (mined) stones

Myanmar (Mogok) historically sets the benchmark; Mozambique now supplies much of the fine material; Thailand/Cambodia, Madagascar, Tanzania and Afghanistan also produce. US import rules on Burmese ruby have changed over time — ask about documentation.

Carat weight and size

Fine rubies over 1 ct are scarce and over 3 ct rare, so price per carat jumps sharply with size. Most commercial rubies are under 1 ct.

Prices per carat

Commercial heated ruby: roughly $100–$1,500/ct. Fine heated 1–3 ct: roughly $3,000–$15,000/ct. Top unheated Burmese or Mozambique: can exceed $20,000–$100,000+/ct at auction. Lead-glass-filled ruby: often under $50/ct. These are indicative retail ranges per carat gathered from published trade and auction reporting; real prices vary widely with colour, size, origin and treatment, and are not a Riakoob quote.

Natural vs lab-grown (synthetic)

Lab ruby (flame-fusion since 1902, plus flux and hydrothermal) is chemically identical corundum and typically costs about $1–$500/ct depending on method; flux-grown stones cost more. Experienced labs can separate them. Under US FTC guidelines a lab-made stone must be clearly described as laboratory-grown, laboratory-created or synthetic, never simply by the gem name.

Treatments you must know about

Heating is common and widely accepted. Lead-glass (composite) filling is a heavy treatment that greatly lowers value and durability. Diffusion and fracture filling also occur. Treatment disclosure is required; ask for it in writing and on the lab report.

Certification

For significant ruby purchases, ask for a report from an independent lab such as GIA, AGL, SSEF or Gübelin stating natural or synthetic origin, any treatments and, where relevant, geographic origin.

Care and durability

Very durable for everyday rings. Glass-filled stones can be damaged by heat, acids and even lemon juice — avoid ultrasonic cleaning for them.

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