"Amorphous" literally means "without form", but, of course, these materials have a form--> it's just not highly regular and predictable, nor is it expressed outwardly by the formation of crystals. Some examples of amorphous gems are: the natural glasses, amber, jet, opal, and "metamict" minerals.
Amorphous Organics
A number of organic gem materials have an amorphous structure. Species like amber and jet which are composed of organic molecules, (those of evergreen tree resin, and the wood of certain hardwood trees, respectively) which have been altered into a near "plastic" polymeric state by geologic forces and time, are examples.
Metamict Minerals
Most zircon specimens that you will see, are crystalline gems, but a few pieces (generally a dull olive green color) have lost some, or all, of their crystalline structure, and have become disorganized internally to a glassy state. This transformation is due to the effects of radiation, and such a material is said to be "metamict".
The radiation source is usually from impurities within the zircon itself, but can be from surrounding rocks. This phenomenon can occur naturally in several minerals, but zircon, and perhaps ekanite, are the only ones of gem significance. These glass-like zircons (sometimes called "low" zircons) do not have the same super-bright luster and brilliance of the crystalline type, and are mainly sought as curiosities by collectors.
Natural Glasses
The atoms making up a glass (either natural or man-made) have been cooled from the molten state so quickly that they fail to assume a regular crystalline pattern. A volcanic glass, like obsidian, then, might be formed if a volcano released lava into the air or water such that it was very rapidly cooled--> this very same lava could, upon slower cooling, form a crystalline material (like basalt, for example).
Obsidian ranges in color from light yellow through brown to black and can be transparent, translucent, or opaque. Those of our ancestors, who lived in areas of volcanic activity, made ready use of these natural glasses
In some cases, due to the presence of other minerals with different crystallization temperatures, when the molten material cools, crystal inclusions may be formed. These can give the obsidian an interesting pattern, or affect the structure in such as way as to cause an optical phenomenon, like iridescence.
Rainbow crystals
are crystals which have an internal fracture catching the light in these crystals produces an exquisite rainbow. Light bringers they have the gift of joy and optimism. The presence of all colors in the rainbow makes them an excellent crystal for chakra work.
