Holly Jolly CrystalThe colors red and green are a common combination on Christmas going back centuri

Holly Jolly CrystalThe colors red and green are a common combination on Christmas going back centuries. Scholars have several theories about the exact origin and the color combination may in fact have sprung up in several places, including colors painted on different sections of medieval churches in Great Britain and red fruit that were hung on the branches of pine trees in Germany.This nearly red-green crystal seemed an appropriate fit for this color scheme. This is a “Watermelon tourmaline”, photographed from the collections at the Natural History Museum in London. Tourmaline is a complex mineral; structurally it forms a series of rings that climb upwards in one dimension, commonly creating crystals that are long in one direction. Tourmaline includes elements like boron and sometimes lithium in its structure, in addition to common elements like silicon, oxygen, iron, and magnesium.This combination of elements is commonly found in igneous or hydrothermal systems and many tourmalines grow in that setting. Because many different elements can fit into the tourmaline structure, many different crystal colors are possible.Pink to reddish tourmaline, as found on one edge of this crystal, is commonly produced when the crystal takes some of the element manganese into its structure. If manganese in the tourmaline structure is exposed to radiation, as naturally occurs in minerals such as feldspars which contain radioactive potassium, the radiation can cause a change in the electronic configuration of the manganese, putting it in a state where the interaction with light gives it a brilliant pink color.The green color in tourmalines is typically produced by iron, sometimes with associated titanium, in the crystal structure. The zoning pattern of pink into green seen in watermelon tourmalines typically expresses a change in the surrounding chemistry as the crystal was growing, leading to iron entering the tourmaline structure instead of manganese.-JBBImage credit: Kotomi Creationshttps://flic.kr/p/axjrgUReference:http://elements.geoscienceworld.org/content/7/5/333.fullhttp://bit.ly/1TUuhekhttp://bit.ly/1YyKPt8 -- source link

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