LIMONITE	The Mineraloids Class		MERCURY
OPAL			OBSIDIAN	TEKTITE	AMBER

The members of the (unofficial) Mineraloids Class are often mistaken for minerals and are sometimes classified as minerals, but lack the necessary crystalline structure to be truly classified as such. Pearl, jet and amber are in addition the products of organic process that further remove them from full mineral status. These materials are found naturally, some are treated as gemstones and are included in most mineral references (which is why we decided to include them here!).

Some of these are included elsewhere even though they are not considered proper minerals (exactly why is listed below).