What is Geode?
Geodes are geological occurrence of minerals in particular form after a particular process. They are formed within volcanic and sedimentary rocks. They are usually hollow inside, shape is usually circular in which there are formed lot of crystals or mineral matters. Crystals formation appears because of the filling of vesicles by minerals deposited from hydrothermal fluids in volcanic alonwith sub-volcanic rocks. They can also form by the dissolution of syn-genetic concretions and partial filling by the same or other minerals precipitated from water, groundwater or hydrothermal fluids.
Cavities are where Geodes can be formed. Or one can say Geodes can appear in any type of cavity. However , the term is usually reserved in igneous and sedimentary rocks for more or less rounded formations. They can also appear in glass bubbles in igneous rocks. An example is vesicles in basaltic lava. They can also appear in rounded cavities of sedimentary formations. Like which is in the American Midwest. On the inside surface after rock sourounding the cavities, Where dissolved silicate and some other minerals like corbonates get tigather. Slowly and steadily the matter get strength and hardens. With the passage of time, these slow process of minerals constituents from groundwater. Where crystals are formed with the help of inside the hollow chamber.
What gives them their color?
Geodes colour composition or formation of colours are results of variable impurities and coloration. Mostly Geodes have crystals like quartz such as Citrin, clear quartz , amethyst. Colour composition is same as normally amethyst or Citrin will have. There are also other Geodes with agate, jasper banding , calcite crystals, chalcedony , dolomite, celestite etc. One can not judge about inside formation of held untill it is broken or sliced into two pieces. Apparently, all geodes will look same having same colour, pattern.
Geodes comes with natural colours but people paint the geodes also or treat the crystals inside to enhance deep colours. Some are dyed to give them brighter look with more intensity of colours. Geodes are being used in various ways such as decoration art, tables, walls , flooring, slabs etc. Adding colours increase the art.