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What to look for

Under 10x loupe in immersion: curved parallel lines flowing through the stone in sweeping arcs, like curved tree rings.

What it means

Curved striae are a strong indicator of flame-fusion synthetic growth. Natural stones generally have straight or angular growth planes rather than curved boule-growth lines.

Expert move

Immersion is often necessary to see subtle striae. If clear curved striae are present, suspect synthetic origin.

Gemstone inclusion

Curved Growth Striae, Synthetic ID

Under 10x loupe in immersion: curved parallel lines flowing through the stone in sweeping arcs, like curved tree rings.

Category Synthetic

Seen in

Synthetic Corundum Chrysoberyl (flame fusion)

Check with

Immersion microscope 20x to 40x fiber optic

Reading order

Confirm the feature is internal, not surface dirt or polish marks.
Use side light to reveal relief, planes and shimmer.
Compare with related stones before making an origin or treatment call.