Goldstone: the glass that sparkles
Goldstone is not mined. It is made in a furnace, and the glitter grows inside the glass as it cools.
Goldstone is a man-made glass. To make it, glassmakers melt glass with copper and hold the batch at a carefully controlled temperature with very little oxygen. As it slowly cools, the copper comes out of the glass as millions of tiny, flat, triangular and six-sided crystals. Each one catches the light, and together they give goldstone its glitter.
The method is usually traced to Venetian glassmakers in the 1600s. A popular story says monks made it by accident, which is where the name monk's gold comes from, but there is no good evidence for that. Its Italian name, avventurina, comes from the word for chance, and it later gave its name to the natural stone aventurine, which has a similar sparkle.
The classic colour is a warm reddish brown. Blue and green goldstone are made in a similar way with other metals in the mix, such as cobalt or chromium, which change the colour of the glass. Blue goldstone, deep blue with silver-white sparkle, is often sold as a night-sky stone.
Because it is made, not mined, goldstone looks the same from batch to batch. That is useful for jewellery makers who need to match beads on a restock. It is a decorative material, and it should be sold honestly as man-made glass. Customers who know that still buy it, because the sparkle is the point.
Not mined, but made. The glitter grows inside the glass as it cools.
