How to Read a Gübelin Report

Every extraordinary gemstone arrives with a question: how do we know? The answer, for over a century, has been the independent laboratory, and among laboratories, the Gübelin Gem Lab of Lucerne holds a particular authority in coloured stones. Its reports are terse, precise documents. Knowing how to read one is a collector's first skill.

Identity before beauty

A report begins by establishing what the object is: species and variety. For the Star of Genesis, the finding reads natural corundum, colour change star sapphire. Each word is load bearing. Natural excludes synthetic material grown in laboratories. Corundum is the species; star sapphire the variety, announcing the phenomenon; colour change a second phenomenon, independently verified.

The measurements

Weight and dimensions anchor the stone's identity: 48.95 carats, 21.65 by 16.80 by 13.16 millimetres, cut as an oval cabochon. No two stones share these numbers together with the report's photographic record; the document and the object verify one another permanently.

Origin

Origin determination is the laboratory's quiet triumph. Trace element chemistry and the character of inclusions carry the fingerprint of the deposit where a crystal grew; decades of reference collections allow the laboratory to conclude, in this case, Burma (Myanmar), the classic source of fine star sapphire, and the origin collectors weight most heavily.

No indications of heating. Five words that can multiply a stone's rarity many times over.

Treatment

Most corundum on the market has been heated to improve colour. The report's finding for the Star of Genesis, no indications of heating, states that its colour and its star are entirely the work of geology. Untreated stones of scale and quality form a small fraction of a small fraction; this line, more than any other, separates categories of rarity.

The rating

Beyond the report itself, Gübelin issues a Gemstone Rating: a single figure out of one hundred synthesising quality and rarity. The Star of Genesis rates 93.7, Outstanding. A rating is not a price; it is something more durable, a scientific ranking that travels with the stone forever.

What a report is not

A gemmological report is not a valuation, not a guarantee of future worth, and never a substitute for the stone itself. It is the foundation on which everything else, connoisseurship, comparison, ultimately conviction, is built. Genesis presents its important stones with their full documentation, and encourages every collector to begin there.