This quality unset boulder opal comes from the Western Queensland fields. Stones like this are becoming rarer as the opal fields are running out.
The price of the stone, unlike many gemstones, is influenced by supply and demand, not by international cartels who agree on price increases.
Size: 37×21 mm (approx 1 1/2″ long) Total Carats: 64.55 Shape: Rectangle Origin: Winton or Quilpie Australia Shipping: Free to your door or post office box by registered mail. Packaging: Black velvet pouch or gem box
Hence, it is destined to go up in value as the supply becomes more restricted which is happening at present. The color of these Black boulder opal stones is completely natural, in contrast to diamonds [for example] which depends on man-made facets to reflect the spectrum colors.
Many of them are presented with some of their ‘mother’ ironstone showing in the foreground. This often adds to the interest of the opal piece because the patterns and shapes that present themselves often stimulate the imagination, much like the clouds in a clear blue sky.
Some of these lovely pieces conjure the imagination and can be called ‘picture’ or ‘personality’ opals. In this case, the ironstone shows brilliant flecks of gem color, against the ironstone and are like stars in the sky. The ironstone ‘mother’ holds the ‘baby’ which is the opal. Hence the term: ‘matrix’ (mother).
Boulder is from Queensland and is also a variety of black if it is found with a dark or black background similar to Lightning Ridge Black opal. The opal appears as veins in often very large boulder ironstones. The color is exposed with the use of diamond saws and wet grinding equipment. Some boulder opals are quite small in the shape of nuts as is the case in the famous Yowah opal fields.