The bands of colour are produced with alternating silica minerals – quartz and morganite – and leave behind bands that lie parallel to one another. Once it evaporates, it leaves behind traces of minerals and calcium carbonate which causes its intricate bands of varying colours. When spring or groundwater featuring dissolved calcite in it drips and evaporates from the ends of stalagmites and stalactites. Calcite is the same mineral that makes up limestone, travertine and marble. Onyx is naturally formed from calcite in caves or bedrock openings around the world. This property has, historically, made onyx a popular stone to use for engraving techniques as well as producing cameos, where a raised relief is produced to form a design that is lighter than the layer it sits on. Brown and white onyx is usually referred to as sardonyx, while the red and white variation is recognised as cornelian onyx.Īll forms of onyx gemstone feature multiple layers, with the lighter layer of stone sitting on top of the darker layer. However, onyx is also found in brown, red and white variations. Most people associate onyx gemstones with a jet black colour with some contrasting white layered bands.
Onyx stone properties how to#
However, there’s so much to know about this amazing stone – including its different colours (yes, it’s not all about black onyx), its durability, its value and how to tell a real black onyx stone from the rest.
Black onyx, in particular, is a hugely popular gemstone. Its stunning layers give it a strikingly dramatic look, which has understandably made it a go-to choice in jewellery making. Onyx is a variety of gemstone that comes from Chalcedony – a silicate mineral, mostly made of calcite (similar to marble and granite), which usually features contrasting layers of colour.
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