Goldstone

In affiliation with GemologyOnline.com
From The Gemology Project

A man-made material usually cut en cabochon. Goldstone consists of minute tetrahedral crystals of copper dispersed in glass. It is created by the melting of glass containing copper salts in a reducing (oxygen depleted) environment, causing the copper salts to decompose to metallic copper. Goldstone has been produced in reddish-brown, blue, purple and green colors; the color of the first is a result of the finely disseminated copper crystals, while the color in the latter three resulting from changes in the body color of the glass surrounding the microscopic copper crystals.

Goldstone was developed by Vincenzo Miotti, a member of a prominent family of Venetian glass makers, in the late 17th century. Keeping with the tradition of the medieval craft-guild, the formulation was maintained a closely guarded secret. It was not until the early 19th century, after the family had stopped making glass, that it was divulged by one of the surviving members of the family. A litany of apocryphal “urban folklore” mythologies regarding how and when goldstone was created have devolved (rather than evolved). Foremost among these is that it was accidently discovered by Italian monks (religious order unknown) when they dropped copper shavings into a batch of molten glass in the 19th century (or 18th century. Or 17th century). Another more apotropaic claim has been advanced that “goldstone” was the result of medieval alchemists’ search to create gold.

Synonyms: “Aventurine glass”

Contents

Diagnostics

Goldstone could be confused for aventurine quartz and sunstone.

Aventurescence

The glittery, glimmering appearance caused by the reflection of light by internal particulate inclusions in both rough and cut stones – is the hallmark of goldstone.

Luster

Greasy

Fracture

Conchoidal to subconchoidal

Refractive Index

1.53

Specific Gravity

Variable from 2.50-2.80

Magnification

Gas bubbles are sometimes evident. The uniform shape and size of the copper crystals as well as the uniform distribution of the copper crystals through the glass body helps differentiate goldstone from aventurine quartz and sunstone. The copper crystals in goldstone are readily visible under 20x magnification. The crystals may appear more silvery than coppery red in the blue, purple and green variations of goldstone as a result of the filtering effects of the colored glass comprising the body of the material. Large masses of rough may sometimes preserve flattened contact surfaces, rounded edges, and surfacial flow lines that were created when the molten glass was poured out onto a hard surface to chill.

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