Goldstone. You know it, that gorgeous with a glittering star field that comes in blue, red, green or purple. It’s used for jewelry. It looks wonderful on your desk as a paperweight, or on a shelf as an eye-catching display object. Kids love it because of the sparkles. Adults love it too – take a deep look into a dark blue example and after a few moments you lost in what feels like the star field in the opening of Star Wars. But what exactly is Goldstone, and were does it come from? What mine do they dig the stuff out of?
Well, as it turns out, it comes from no mine. Even though it sure likes an amazing example of mother nature’s artistry, perhaps helped along with human assistance and a tumbler, it is actually man made. That’s right, it is synthetic. But not synthetic in a bad way, and certainly not synthetic in the modern sense such as with Ruby, which is created by fusing potash alum at a high temperature with a little chromium as a pigment. No, Goldstone is no lab or factory born. It’s birth is traced to the hand of the artist and artisan. But before we look at origins, let’s look at exactly what Goldstone is.
What is Goldstone?
Goldstone is form of man-made glass. It has a glittering, metallic character luster caused by flat faced and highly reflective inclusions of copper. The luster is caused by heating molten glass to the temperature necessary to dissolve copper oxide granules added to the molten glass. The melt is then cooled slowly allow the copper ions to grow into uniformly dispersed octohedral shaped crystals. The size of the copper crystals formed is directly related to the length of time taken to coll the melt. The longer the cooling, the larger the crystals. It is these copper crystals that creates the glittering luster.
But wait, you ask. What make gives the goldstone it’s red, or blue, or green, or purple color in which the copper stars are fixed? Well, the answer to that differs with each color of goldstone. Glass itself is typically colorless, and goldstone is no exception. Red goldstone is red because of reflection off the copper crystals. Blue, green, and purple goldstone use metals other than copper, but the background color doesn’t come from the metal, but rather from the addition of other elements to the glass itself. The blue in blue goldstone is caused by the addition of cobalt to the glass, green from the addition of chromium, and purple from the addition of manganese. Goldstone without copper is easier to work with when reheated, because of less stringent reduction requirements and higher melting points of manganese and cobalt.
Regardless of the metal used to create the particular color of the star field pattern, the glitter effect is intensified when a piece of goldstone is moved under light, when a lighting source is moved over the goldstone, or when the observer is in motion relative to a piece of lighted goldstone. If that sound technical, then think of it like this. A lighted piece of goldstone gets a whole lot glitterier if either you move it, you move yourself, or you move the light.
History of Goldstone
Goldstone dates as far back as the period between the 12th and 13th centuries A.D., the earliest known goldstone object being an amulet excavated in Iran with an inscription dedicating it to one of the rulers of Syria during that period. It was being manufactured in Italy by the 17th century, in Murano and Venice. The Motti family of Venice was granted an exclusive license to manufacture the material by the Doge (think “Duke”, they both originate from the same word) of Venice. The Chinese were making goldstone around the same time as the Italians with bottles made of the material by the Imperial Workshop handed out by the Qing Emperor’s court as gifts and rewards.
Goldstone is actually a more recent name for the material. An earlier common name for it aventurine glass, based on the Italian “avventurina” meaning “by chance” or “accident” in reference to the tale that the discovery of how to make the material was an accident. Goldstone should not be confused with the mineral aventurine, which is a feldspar or quartz with a mica inclusion that can also be glittery. In point of fact, the mineral was named after the goldstone because it’s glittery luster was reminiscent of of goldstone.
Party Tricks with Aventurine
So the heading is a bit of joke – there will be no party tricks discussed here. Instead let’s talk a little bit more about the name aventurine, the early name for goldstone. Besides gifting it’s name to the natural mineral aventurine, goldstone has lent it’s original to several technical terms used to describe that glittery loveliness goldstone is in possession so much of.
First is the term “aventurescence” which refers to the phenomena that occurs when a material with light-reflecting particles that produce a sparkly or glittery luster.
Then we have the term “aventurescent” which describes (also see the definition of adjective) materials that exhibit the phenomena of aventurescence. Usage examples include: aventurescent quartz, aventurescent feldspar, aventurescent iolite, and aventurescent soda pop. Actually that last item is joke, but soda pop beside shimmery and bubbly right after pouring does remind one of goldstone, well, a bit.
Cousins of Goldstone and Other Curious Facts
There are other types of glass that have some similarity to goldstone. For example, there is transparent red copper ruby glass and also opaque “sealing wax” purpurin glass, all of which have beautiful reddish colors of which are created by colloidal copper. The key difference among these is the size of the copper crystals. Goldstone has macroscopic (large) reflective crystals; purpurin glass has microscopic (small) opaque particles; copper ruby glass has submicroscopic (very small) transparent nanoparticles.
The outer layers of a batch of goldstone often has a duller color and less glittery goodness, characteristics usually dues to poor crystallization which decreases the size of the reflective copper crystals and makes the surrounding glass more opaque with non reflective particles. This may also be due to partial oxidation of the copper which may lead the crystals dissolving leading to a transparent blue-green glass.
Sometimes goldstone only displays the glittering effect from two directions rather than from any vantage point.
Goldstone is actually popular for cutting jewelry. As rough pieces, it is usually sold as broken chunks and as slabs suitable for cutting cabochons. Smaller pieces might be rock tumbled, while larger chunks might weight over 50 pounds. A single batch of goldstone usually weighs in at 100 pounds or more, before being cut into smaller chunks. The quality of the goldstone due to variability from the manufacturing process will dictate the end use.
Metaphysical, Spiritual, and Healing Properties of Goldstone
Even though goldstone is synthetic, many believe it has spiritual or metaphysical properties, and can be used in physical healing. The specific properties and effects of the goldstone vary depending on who you consult, and their particular perspective. One thing is certain, contemplating the start field of a beautiful example of goldstone can be a calming and meditative experience!
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Top photo depicting a piece of ‘red’ or ‘brown’ Goldstone glass under magnification to show the crystals inside – by Albionfireandice – website, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=104498606