Geological Wonders: Crystal Cave of the Giants

Found deep inside a mine in southern Chihuahua Mexico, these crystals were formed in a natural cave totally enclosed in bedrock. A geode full of spectacular crystals as tall as pine trees, and in some cases greater in circumference, they are a translucent gold and silver in color and come in many incredible forms and shapes. 

The Crystal Cave of the Giants was discovered within the same limestone body that hosts the silver-zinc- lead ore bodies exploited by the mine and it was probably dissolved by the same hydrothermal fluids that deposited the metals with the gypsum being crystallized during the waning stages of mineralization.

Geological Wonders: Sahara Eye

This spectacular landform in Mauritania in the southwestern part of the Sahara desert is so huge with a diameter of 30 miles that it is visible from space. Called Richat Structure --or the Eye of the Sahara-- the The formation was originally thought to be caused by a meteorite impact but now geologists believe it is a product of uplift and erosion. The cause of its circular shape is still a mystery.
 

Geological Wonders: Blue Lake Cave

Mato Grosso do Sul region in Brazil (and especially the quiet town of Bonito) boasts many marvelous underground lakes: Gruta do Lago Azul, Gruta do Mimoso, Aquário Natural. The world famous "Gruta do Lago Azul” (Blue Lake Cave) is a natural monument whose interior is formed by stalactites, stalagmites and a huge and wonderful blue lake. The beauty of the lake is something impressive. The Blue Lake Cave has a big variety of geological formation but impresses mainly for the deep blue colored water of its inside lake.