As precious gems go, opal is one of the most visually striking options on the market. It comes in just about every colour imaginable. These stones are comprised of microscopic spheres of hydrated silica — the same material found in sand.
Over time, moisture gets trapped inside the silica in amorphous patterns. As a result, the stone refracts incoming light and produce a playful display of colours known as opalescence — hence the name.
So are all opals alike?
Well, not quite. While they all share the same mineral structure, opals differ in quality depending on its clarity and the colour of the host rock. There are four broad classifications of opal — crystal, black, white and boulder. All of them exhibit different levels of opalescence.
While recent fashion trends have led to synthetic opals, it cannot be denied that genuine ones are of a much higher quality and opalescent value.
So, what type of opal should you get for your jewellery collection?
Crystal opals are best in terms of transparency which is an essential quality for producing variations like fire and water opals. This is thanks to its high lucidity, which creates an intense diffracted glow.
Crystal opals are one of the few types of gemstones that can be faceted before being set into a piece of jewellery. This makes them ideal for producing opal earrings, pendants, rings, and other kinds of fine jewellery
Black opals are considered one of the rarest types of gems and are highly sought after on the market. As a result, they tend to fetch a high price in exchange for its high opalescent value.
As the name implies, the host rock for dark opals is of the darker variety — usually grey, black, brown or blue. These rocks serve as the perfect backdrop for showcasing the marvellous display of colours inherent in opals. Many describe the appearance of black opals as an intense storm behind a rainbow of colours.
The beauty of black opals is best displayed in full view. Hence they are often used as cabochons (shaped and polished) for larger jewellery pieces. Its’ aesthetic value is significant enough to rival diamonds. It is often used on luxury jewellery pieces like engagement rings and wedding pendants.
White opal may be one of the most common types of gemstones, but that doesn’t make them any less valuable. They exhibit a pearly white appearance, which ranges from transparent to completely opaque.
The more opaque the stone is, the lower its’ opalescent value but that’s not necessarily a bad thing; some people actually prefer it. Nevertheless, white opals shine best when viewed in direct sunlight. Its’ pale appearance and affordable price make it a popular choice for everyday jewellery pieces.
As the name suggests, boulder opals are a type of gemstone with only a few of its host rock still connected. They are often used in jewellery as thin segments or shapes to complement jewellery centrepieces.