Stunning fire agateThe irridescent effect of the most beautiful of agates is caused by the same phen
Stunning fire agateThe irridescent effect of the most beautiful of agates is caused by the same phenomenon that makes a thin layer of petrol shimmer in glowing colours on a puddle of water, called thin film interference. It is similar to the glows of opal, in that the colours change as the stone is rotated under a light source, but caused by a different interaction of light with contrasting mineral organisation in silica. The colours are due to interference between the light rays reflected from layers of different composition within the agate that are of a similar size to visible light wavelengths. Thicker layers produce reds and greens, and thinner ones the rarer blue and violets.It is found in the southwest USA, Mexico and Brazil and formed in a hydrothermal geological environment from hot mineralised fluids precipitating silica and iron oxide when encountering changed conditions. These resulted from huge circulating cells of heated waters deep in the Earth interacting with magmas.Another kind of agate gifted with similarly beautiful optical effects due to a different phenomenon is iris agate, discussed in a post here: http://tinyurl.com/qj47hjoLozImage credit: Jessa DowAnderson Cooper -- source link
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