Synthetic Opal .Opal is naturally-occurring silica-based amorphous solid known for its flashes of fire colour. An amorphous solid is a material that, unlike crystal, is not organised in a regular lattice pattern. This makes for some unusual interactions with light and is explicable for opal’s rainbow colours. Natural opals are rare and very expensive when they display a good play of colour. For this reason and to give consistency in our ranges, we choose to use lab-created opals for our jewellery. These synthetic opals are manufactured in Germany and often have a non-directional play-of-colour presenting as irregular and non-directional swirls.