What are Geodes?
Geodes are subspherical rock structures with an internal cavity lined with mineral materials. They are the sedimentary and volcanic rock that is hollow, consisting of mineral matter (may or may not include crystals). Geodes are covered and protected with a durable outer wall resistant to weathering than the surrounding bedrock.
You cannot judge by looking at the rock from outside Geode or some ordinary rock. One of the most common aspects found in all Geodes is their round shape, which induces a wow effect.
Structure of Geodes
Geodes are characterized by a light greyish translucent shell that is internally lined with crystals, sphalerite, quartz, pyrite, barite, and dolomite. Amongst all of them, the most common mineral found in Geodes is Quartz.
Colour of Geodes
Geodes are hollow rocks that are originated and formed from sedimentary rocks. As we know that these rocks are lined with crystals, the crystal cavities are filled with fluid during different precipitation stages.
Hence, we can conclude that the rock undergoes various colours during its formation due to the changes in chemistry experienced in the environment.
Geodes Occurrence and Formation
Geodes are rocks that are usually found in large numbers, especially in areas of the geochemical environment. In these areas, apart from geodes, many other rocks are also formed. The localities of geodes are also found in the areas of:
a) Stratified volcanic deposits such as tuffs and basalts.
b) Stratified sedimentary carbonate deposits such as dolomites and limestones.
What regions have the highest concentration of Geodes?
They are mostly found in the USA, including Utah, California, Indiana, New Mexico, Arizona, and Ohio. Other countries where high concentrations of the Geodes can be found include Brazil, United Kingdom, Mexico, and Namibia.
Geodes with Volcanic origins
At the time when a volcano erupts, they release various types of lava. Numerous gases are mixed within the lava. As soon as the lava cools down, the bubbles are formed. These bubbles get converted into a solid crystalline round-shaped Geode.
Geodes with sedimentary origins
The bubbles could also be formed in the empty spaces of shells, tree roots, and animal burrows. Over a while, the sediments are filled in these hollow remains, and eventually, the surrounding earth hardens into rock.
Can heat change its colour?
Yes, a lot of heat can change Geode’s colour. It has been analyzed that a geode changed its colour from Purple to light Yellow or citrine when it is brought closer to excessive heat. It is one of the reasons why geodes are found in a wide array of colours.