Which Gemstones Appreciate? The “Three Blues” Rule Explained

Intro

The “Three Blues” rule is a simple buying heuristic: blue sapphires, tanzanite and Paraíba tourmalines are the three blue gemstones that most often hold or increase value over time. It isn’t a guaranteed investment plan. Instead, it’s a shorthand that points to three stones whose color, rarity and market forces give them a historically stronger chance of appreciating than many other colored gems. Below I explain the why and how—what to look for, what reduces value, and how to apply the rule if you’re buying jewelry or loose stones.

Why blue matters

Blue is a historically desirable hue. It reads as rare and vivid at many price points, from light aquamarine blues to saturated royal blues. But color alone doesn’t create investment-grade value. Appreciation depends on a combination of:

• Rarity: single-source supply (tanzanite) or extremely limited production (Paraíba, blue diamonds).
• Quality of color: tone and saturation—vivid, medium-dark blues usually command premiums.
• Size and clarity: larger, eye-clean stones increase disproportionately in price.
• Treatment and disclosure: untreated natural stones, or stones with market-accepted treatments and certificates, sell for more.
• Provenance and certification: origin (Kashmir, Ceylon, Merelani) and lab reports (GIA, AGL, SSEF) increase buyer confidence and liquidity.

The Three Blues—what each one is and why it can appreciate

1. Blue Sapphire (corundum)

Why it can appreciate: Sapphires have millennia of desirability and significant collector demand. Certain origins—Kashmir, classic Ceylon (Sri Lanka), and specific Burmese stones—are rare and command large premiums. High-quality, untreated sapphires with strong, velvety blue saturation and good transparency are scarce.

What to look for: For investment potential, aim for natural, untreated or well-documented heat-treated stones with a laboratory report. A 2–5 ct eye-clean sapphire with vivid medium–dark blue color from a respected origin can command a strong price per carat. Kashmir and high-grade Burmese sapphires often fetch the highest per-carat prices; their scarcity is the main driver of appreciation.

What reduces value: heavily included stones visible to the naked eye, weak or grayish blues, or undisclosed dyeing/filling. Lab-grown sapphires also suppress prices at lower tiers, so provenance matters.

2. Tanzanite (zoisite)

Why it can appreciate: Tanzanite is found almost exclusively in the Merelani Hills of Tanzania. That single-source supply creates a built-in scarcity narrative: if the mine’s output declines, supply tightens. The gem’s vivid blue-violet hues—particularly stones with strong blue and minimal purple—are highly sought after in larger sizes.

What to look for: Vivid blue-violet stones with good saturation and clarity in the 2–10 ct range tend to show the best appreciation potential. A 5 ct vivid tanzanite can be far more valuable per carat than many similarly sized stones at lower quality. Request a certificate and confirm natural origin.

What reduces value: tanzanite is commonly heat-treated to bring out the blue; that treatment is widely accepted, but stones with brownish tones or poor clarity will underperform. Tanzanite’s market is more trend-driven than sapphires, so prices can be more volatile.

3. Paraíba Tourmaline (copper-bearing tourmaline)

Why it can appreciate: Paraíba tourmaline—originally discovered in Paraíba, Brazil—displays an electric neon blue-green color caused by copper and manganese. These stones are extremely rare; fine examples command some of the highest per-carat prices among colored gems. Brazilian Paraíba deposits are limited; African Paraíba-like stones exist but Brazilian provenance is most prized.

What to look for: Small stones (1 ct) with vivid neon blue-green color and strong clarity can already be very expensive. Larger, eye-clean stones with Brazilian origin are the most likely to appreciate significantly. Because supply is tiny, market demand strongly influences prices.

What reduces value: stones with weak color, brownish tones, visible inclusions, or uncertain origin. Many tourmalines are heated or clarity-enhanced—full disclosure is essential.

Blue diamonds: an outlier

Blue diamonds deserve mention even though they are not one of the “Three Blues” in most trade usage. Natural fancy vivid blue diamonds (Type IIb) are among the rarest and most expensive gems on earth. Their appreciation history is strong, but the entry price is extremely high and the market is specialized. For most buyers, the Three Blues—sapphire, tanzanite, Paraíba—are more practical.

How to apply the rule when buying

• Buy natural with documentation: insist on a reputable lab report (GIA, AGL, SSEF) that states treatment and origin. Undisclosed treatments destroy resale value.
• Prioritize color and eye-clean clarity: for blue stones, color quality drives value more than small differences in cut. A 2 ct vivid blue stone often trades for several times the per-carat price of a 2 ct, duller stone.
• Choose size strategically: prices jump at certain benchmarks (2 ct, 5 ct, 10 ct). If you want appreciation, aim for sizes that the market prizes, not just oddball sizes.
• Prefer classic settings and metals: blue gemstones typically pair well with 18k white gold or platinum. A neutral, high-quality setting preserves perceived value and broadens appeal to buyers.
• Consider liquidity: sapphires tend to be more liquid than Paraíba at many price levels. If resale is important, choose stones with widely recognized provenance and documentation.
• Diversify and buy what you love: even if you’re focused on appreciation, buy stones you enjoy wearing. Markets are cyclical; having personal enjoyment reduces regret if values stall.

Common pitfalls

Don’t buy based on color photos alone. Beware of misrepresented origins or undisclosed treatments. Avoid stones without certificates once you’re paying mid to high prices. And don’t expect rapid gains—appreciation in colored gems is usually a multiyear to multidecade play tied to supply changes and collector demand.

Bottom line

The “Three Blues” rule is a useful starting point because sapphire, tanzanite and Paraíba tourmaline combine strong color appeal with scarcity factors that support appreciation. But quality, documentation, size and treatment determine real-world outcomes. If you want potential appreciation, buy natural, well-documented stones with vivid color and eye-clean clarity, and think long term.