Diamonds and gemstones · 12 Sept 2026 · 1 min read

Aquamarine and yellow sapphire: how to choose a coloured stone

The two centre stones of the Bright Pearl collection differ in hardness, treatment and wear. Four criteria for choosing the right coloured stone.

Written by Kim Bảo Minh Châu

Close-up of the Honey Drop necklace with a pear-cut yellow sapphire

The Bright Pearl collection by Kim Bảo Minh Châu uses two coloured centre stones: sea-blue aquamarine and honey-toned yellow sapphire. Both are pear cut, haloed with melee diamonds in 18K white gold.

The two stones

	Aquamarine	Yellow sapphire
Mineral family	Beryl, like emerald	Corundum, like ruby
Colour	Pale blue to sea blue	Lemon to honey yellow
Mohs hardness	7.5 to 8	9
Common treatment	Heat, for a clearer blue	Heat, for even colour
Everyday wear	Yes, avoid hard knocks	Very durable, second only to diamond

The Sea Blue ring, pear-cut aquamarine with a diamond halo

Four criteria

Colour drives price most. Deeper, more even, brighter colour costs more. Deep blue aquamarine is rarer than pale.
Clarity. Coloured stones often have small inclusions; those invisible at normal viewing distance are acceptable.
Cut. Balanced facets spread colour evenly, with no dark zones or pale "windows" in the centre.
Treatment. Heat treatment is common and stable. Any other treatment must appear on the report, as it affects value and care.

Documents

Coloured centre stones at KBMC come with an independent gemstone report stating species, weight, measurements, colour and any treatment. On buy-back, certified coloured stones count at 50% of the stone price, 70% on trade-in.