Definition of a Mineraloid
A mineraloid is a naturally occurring, inorganic substance with no internal crystalline structure.Minerals are naturally occurring crystalline solids, meaning they're made up of a highly ordered, repeating arrangement of atoms. In a mineraloid, atoms do not come together in this way and instead form a pattern that's random or disorganised.
Minerals and mineraloids have a definite chemical composition and form through natural geological processes.
Examples of mineraloids include obsidian, opal, amber, tektites (such as moldavite), and shungite.
Pearl is sometimes included in broader lists of mineraloids, although it is organic and formed biologically. Strictly speaking, anything that's organic cannot be classed as a mineraloid.
It can be difficult to distinguish a mineraloid from a mineral based on appearance alone because both can have similar physical characteristics, such as colour, lustre, and texture.
(*)The word 'amorphous' describes any material that's non-crystalline, whether it's natural or man-made. Glass is amorphous, but because it's man-made, it's not a mineraloid.
Amorphous is used in various scientific fields to describe a substance that lacks a definite crystalline structure or well-defined shape.
The word 'amorphous' comes from the Greek 'a', meaning 'without' or 'not', and 'morphē', meaning 'form' or 'shape.' When combined, 'a' and 'morphē' create 'amorphos', which translates to 'shapeless' or 'without form'.
Article Pictures
Precious opal: Courtesy of James St. John. Amber, obsidian, and moldavite: Courtesy of Stan Celestian.
