WHY UNHEATED SAPPHIRES COMMAND A PREMIUM

Heat treatment involves heating sapphires to high temperatures (1,400-1,900°C) to improve their color and clarity. This process:

• Dissolves silk (rutile inclusions) to improve clarity
• Intensifies or modifies color
• Removes unwanted color zones
• Can turn pale stones into vivid ones

Heat treatment is permanent and stable. It's been practiced for centuries and is accepted by the trade. However, it fundamentally changes the stone from its natural state.

For a deeper dive on treatments, see our guide on heated vs unheated gemstones.

Nature rarely produces sapphires with ideal color straight from the ground. Most rough sapphires have:

• Color that's too light, too dark, or unevenly distributed
• Silk that creates haziness
• Secondary color tones (green in blue sapphires, brown in pink)

Heat treatment can fix these issues, so the vast majority of rough is treated. Only the finest 5-10% of sapphires emerge from the earth with color and clarity good enough to sell without enhancement.

This natural scarcity — combined with increasing demand from collectors who value "as nature made it" — creates the premium.

The premium for unheated varies significantly by origin:

Note: Premiums vary based on quality, size, and market conditions. Exceptional stones can command even higher premiums.

You cannot determine heat treatment by looking at a stone. Lab certification is essential.

Gemological labs examine internal features under magnification and spectroscopy:

• Intact silk: Rutile needles that would dissolve with heating
• Natural inclusions: Certain inclusions change or disappear with heat
• Spectroscopic signatures: Heat alters the chemical structure in detectable ways

Trusted labs for unheated verification include GRS, Gübelin, SSEF, GIA, and similar accredited institutions. The certificate should explicitly state "No indication of thermal treatment" or "No heat."

Learn more about reading gemstone certificates.

For investment purposes, unheated sapphires offer several advantages:

• Increasing scarcity: As deposits deplete, unheated stones become proportionally rarer
• Collector demand: Sophisticated buyers increasingly prefer "natural" stones
• Auction performance: Unheated stones consistently outperform heated equivalents at major auctions
• Future-proofing: Treatment preferences may shift; natural is always natural

Historical data shows unheated sapphire premiums have increased over time as awareness grows and supply diminishes.

Unheated isn't always the right choice:

• Budget constraints: A beautiful heated sapphire may be preferable to a mediocre unheated one at the same price
• Jewelry use: If you're buying for a ring you'll wear daily, visual beauty matters more than treatment status
• Specific colors: Some colors (like vivid yellow) are extremely rare unheated

Heat treatment is accepted, permanent, and doesn't diminish a stone's beauty. The premium for unheated reflects rarity and collector preference, not necessarily superior appearance.

Everything above applies to rubies as well — with even higher premiums. Fine unheated Burmese rubies with "pigeon blood" color are among the rarest gemstones on Earth.

Unheated ruby premiums can reach 100-200% over heated equivalents for top-quality stones. At auction, the world's most valuable rubies are invariably unheated.

See our Ruby Buying Guide for more on ruby treatments and value.