Mineraloids and their features 

A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids are amorph.

Limonite

Chemical Formula : FeO(OH)·nH2O

Mohs Scale : 4 - 5.5

Obsidian

Green Opal

Chemical Formula : SiO2·nH2O (hydrated silica)

Mohs Scale : 5.5 - 6 


                                 Opal

Obsidian


Limonite

From Egypt


Opal

Limonite

From Egypt

Obsidian


Shungite

Shungite is a black mineraloid made of up to 99 percent carbon. Mohs scale of shungite is around 3.5 -4 


Chrysocolla 

Limonite

Opal

Menilite

Menilite

Opaline concretions found in marls, gypsums and shales. Sometimes considered a variety of opal but probably impure and really just young Flint nodules which haven’t recrystallised to quartz yet; thus really a rock rather than a mineral.