Finding The Ocean Inside An Opal

image credit: Taifighta cc
Opal is a hydrated amorphous form of silica. Because of its amorphous character it is classed as a mineraloid, unlike the other crystalline forms of silica which are classed as minerals.
The internal structure of precious opal makes it diffract light; depending on the conditions in which it formed it can take on many colors. Sometimes, when the light hits an opal, it looks like an underwater scene from the ocean.