Sparkling Glass ball; diameter 30mm, undrilled.
Gold river is not a naturally grown mineral, but synthetically produced Glass.
The fascinating process for producing gold flux was discovered around 1626 by the Venetian glassmaking family Miotto: initially colorless glass becomes sparkling, colored decorative glass that can be cut and engraved by adding metal compounds.
In the absence of air and through very slow cooling, fine copper crystals can form in the melt, which later trigger the sparkle.
Gold river is also known as gold sandstone and aventurine glass. This is derived from the Italian term "per avventura" (by chance) and refers to the unpredictable distribution of the crystals.