Professional Jeweler Archive: Pink Aventurescence

April 2005

Merchandise | Gemology

Pink Aventurescence

Glowing pink surprises adorn this new quartz find from Brazil

By Robert Weldon, G.G.

At first glance, this faceted rock crystal quartz elicits little remark. It appears less than perfect, peppered with dark inclusions. As you step toward it, however, a flash of fuchsia spreads across its surface. Just as quickly, it disappears.

The flash apparently is caused by a host of microscopic, neatly oriented inclusions that flash a uniformly pink interference color when light strikes their surface at specific angles of reflection to the viewer’s eye.

Optical Fairy Dust

This phenomenon is known by the curious name of aventurescence, an optical effect with an equally curious history. Aventuresent quartz is described copiously in gemological literature, but always as being greenish and caused by tiny fuchsite inclusions (green muscovite mica).

Vista Gems, a dealer in Skillman, NJ, showed samples of fuchsia aventurescent quartz at the American Gem Trade Association GemFair in Tucson in February. It was found last year in Minas Gerais, Brazil, but the company won’t disclose the exact location.

Microscopic examination reveals several inclusions. It has hexagonal green crystals (likely muscovite mica flakes) and bright red oxide inclusions known as goethite. The goethite takes on a fern-like appearance and is scattered throughout at odd angles. Exactly what causes the evanescent pink sheen, however, remains a mystery. But it does bring up the story of aventurescence.

The Glass Maker

In the 18th century, an Italian glass blower in Murano, Italy, was melting ingredients in a vat when he accidentally knocked a flask of copper filings into the molten glass. The copper filings created golden spangles in that batch of glass, a form that became widely popular and was often fashioned into decorative items and smaller faceted pieces used in jewelry. The glass became known as a ventura, the Italian phrase for “by chance.” Man-made aventurescent glass remains popular to this day and is called goldstone in the trade.

Decades after the glassmaker’s discovery, natural quartz with tiny green fuchsite inclusions was discovered in Brazil and became known as aventurescent quartz – one of the few occasions where a natural gem was named after a man-made one.

All Photos by Robert Weldon

At first glance this Brazilian rock crystal quartz is unremarkable (top). When it’s moved, a broad pink flash of aventurescence appears (bottom).
Goethite and lepidocrocite inclusions are scattered throughout the gem.
This author believes that oriented hexagonal (and highly reflective) green muscovite mica flakes flash pink interference colors when the light reflects off of their surfaces at certain angles.

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