Inclusions in Gemstones: Flaws or Signatures?
“This stone has an inclusion — is that serious?” A fair question — and the answer may surprise you: in gemmology, inclusions are as much signatures as flaws. Sometimes they even push a stone's value up.
What is an inclusion?
Everything the stone captured as it crystallised: crystals of other minerals, rutile needles, “feathers”, veils, growth zones… They are the gem's geological archive: they tell where and how it formed, millions of years ago.
What inclusions prove
First piece of good news: natural inclusions are the best proof of authenticity. Synthetic stones are usually too clean, or show inclusions typical of the factory (bubbles, curved growth lines). It is by studying inclusions under the microscope that laboratories establish a stone's natural origin… and even its country of extraction: some inclusions are typical of Ceylon, others of Burma or Colombia.
When the inclusion makes the value
- The emerald's “garden”: its poetic inclusions are part of its identity — a perfectly limpid emerald would raise suspicion rather than admiration;
- Silk in sapphires: fine rutile needles give Kashmir sapphires their famous velvety look — the most prized inclusion in the world;
- Cat's eye and star: these are oriented inclusions, and they create those spectacular phenomena in star sapphires and chrysoberyls.
When the inclusion is a genuine flaw
Let us be honest: an inclusion can also count against a stone. The cases to avoid: an inclusion that is very visible at the centre of the table and distracts the eye, a fissure reaching the surface and weakening the stone, or inclusions so dense that they extinguish transparency. It is all a matter of balance: the market standard for coloured stones remains “eye clean” — clean to the naked eye, without obsessing over the microscope.
Our advice as dealers
Do not ask for a stone without inclusions: ask for a stone whose inclusions affect neither the eye nor the durability. That is exactly what we select at the source. Come and study them with us under the loupe at a meeting in Paris — or explore our exceptional gems.
