In April 2025, Sotheby’s auctioned two Brazilian Alexandrite rings. Both were untreated and showcased dramatic color change. Yet one sold for over HKD 1.1 million (~USD $146,000), while the other sold for just HKD 228,600 (~USD $29,000). Here's a clear breakdown of what drove that price gap.

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4.03 ct Alexandrite Ring

Sold for: HKD 1,143,000 | Estimate: HKD 800,000–1,500,000

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3.02 ct Alexandrite Ring

Sold for: HKD 228,600 | Estimate: HKD 180,000–350,000

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1. Size Matters

The difference between a 3.02 ct and a 4.03 ct Alexandrite may seem small—but for rare stones, it's massive. Alexandrite over 4 carats, especially with strong color change, is investment-grade. Size scarcity drives market price, and that’s exactly what we saw in this auction.

2. Clarity and Eye Appeal

While both stones show attractive green-to-purple color change, the smaller one appears to be more included. Visible inclusions can dull the gem’s brilliance and weaken the dramatic effect Alexandrite is prized for. The 4 ct stone appears cleaner and more vibrant.

3. Certification Confidence

The more expensive stone came with reports from both GIA and Gübelin—two of the most trusted gem labs. The 3 ct stone only had GIA certification. For a gem as rare as Alexandrite, dual-lab backing boosts market confidence and pricing. Origin can be a contentious issue, and two reputable reports remove doubt.

4. Color Quality

Photos show both stones have a desirable green-to-purple shift. But photos don’t always capture saturation and intensity. It’s likely the larger stone had stronger saturation and a cleaner shift, making it more valuable—even if the color tone appears close at first glance.

5. What Investors Look For

Investors prioritize size, clarity, and documentation. The 4 ct stone hits all three benchmarks. The 3 ct ring, while beautiful, likely fell short on clarity and paperwork. In rare gemstones like Alexandrite, these differences make or break value.

Final Thoughts

Brazilian Alexandrite remains one of the most prized gemstones for collectors. But pricing isn't arbitrary—it's grounded in observable characteristics like carat weight, clarity, and lab certification. The Sotheby’s 2025 auction reminded us that in the high-value gem world, the top 1% always commands a premium.

While country of origin is prized by some collectors, the most important quality for Alexandrite will always be degree and quality of color change.

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