Goldstone Properties Facts and Photos
1. What is Goldstone?
2. Dispelling the Myths
3. Goldstone and Aventurine
4. Our Collection of Goldstone
What is Goldstone?
Goldstone is a man-made material that's occasionally referred to as aventurine glass. The name is not used quite as often because it implies an association with the mineral aventurine when in fact the two have little in common.
Goldstone is considered to be an imitation of aventurine feldspar also known as sunstone. It's characterised by coarse flecks of copper randomly dispersed within glass.
Although goldstone is usually orange or brown, it can also be navy blue and occasionally green. The colour is generally caused by the presence of copper.
In blue goldstone the copper is replaced by an alternative mineral. This can sometimes alter the colour of the glass which gives the flecks a slightly different appearance. With that said, the glass may also be subtly coloured.
Green goldstone which although quite rare is produced by using chromium oxide. This substance is also used as a green pigment.
The shape and size of the glittery specs in goldstone tends to be relatively uniform. The distribution is rarely as natural as in the minerals sunstone and aventurine.
Dispelling the Myths
The most famous story about how goldstone came about is a dubious tale which gathered momentum through plagiarism. As a result it's now widely believed to be factual.
The real story behind the production of goldstone is very different but just as interesting.
The myth says goldstone came about "by chance" when glass producing monks in Venice accidentally dropped a jar filled with specs of copper into a vat of molten glass. Once the glass solidified it had a fascinating spangly or glittery appearance.
The accident led to the new material being named avventurina from the Italian word "disavventura" meaning "mishap" or "misadventure".
Depending on the article you read, the incident is said to have taken place at some point during the 13th, 17th 18th or 19th century.
Whilst it's well known that an early glass maker from Murano (a group of islands in Venice famous for glass making) attempted to imitate the minerals agate and chalcedony there's no evidence to suggest he produced the material known today as goldstone.
Factual articles that have been written suggest goldstone was created by Vincenzo Miotti a physicist and astronomer born in Murano in 1712.
The exact formula he used was not disclosed until his wealthy glass-making family stopped producing glass. Their reason for finally revealing the formula is believed to have been to kick-start the tradition of manufacturing goldstone once again in Venice.
In the 1860's a new formula was created based on a recipe compiled by French chemist Théophile-Jules Pelouze. In 1894 Henry Stephens Washington visited a glass making factory in Murano and subsequently wrote the following;
The manufacture of this glass being a trade secret I could extract any information from the foreman who gave me the specimens as to the process or details of the manufacture; a fact which is greatly to be regretted.
Having been given some goldstone, he went on to write an account which included specific details about the copper crystals used in its production.
Goldstone or aventurine glass was once again discussed in 1876 by French writer Louis Dieulafait. With regards to the material referred to as aventurine he writes;
For several centuries Venice has had the monopoly of the fabrication of aventurine; and even now, it is a Venetian artist, Bibaglia, who furnishes to commerce the artificial aventurine that is most highly prized. Aventurine is a glass the base of which is soda ash, lime, and magnesia, coloured yellow by oxide of iron, and holding in suspension a large number of small particles of oxide of copper.
The distribution of these particles in a regular manner through the whole vitreous mass appears to be the chief difficulty in its manufacture. The dexterity requisite to accomplish this must be very difficult to attain, for the profits realized from the manufacture of aventurine are remarkably large.
According to its quality the artificial gem sells for $5 to $15 the pound, while the raw materials that enter into the composition of a pound of it are certainly not worth a quarter-dollar. French chemists--M. Hautefeuille in 1860, and M. Pelouze in 1865--have published processes by which productions have been obtained equal to that of Venice, and, in the latter case, perhaps superior.
The new aventurine of M. Pelouze has a beautiful lustre, and a hardness exceeding that of glass and ordinary aventurine. It is obtained by melting together 250 parts sand, 100 parts carbonate of soda, 50 parts carbonate of lime, and 40 parts bichromate of potassium. It will be seen that by this formula the spangles with a basis of copper are replaced by spangles with a basis of chrome.
Goldstone Vs Aventurine
The mineral aventurine is believed to have been named after goldstone. The reason is because it also exhibits a sparkly appearance caused by the presence of plate-like inclusions of other minerals.
This optical phenomenon has become known as aventurescence. As well as being used to refer to minerals like sunstone and aventurine, it's also used to describe the effect seen in the material widely known as goldstone.