Pyrite

Pyrite

and when exposed to the elements over a long period of time can change into the closely related malachite

from the Upper Silurian age

Aquamarine has a hexagonal crystal structure and is highly prismatic

Middle Devion period

These specimens of natural uncut aquamarine occur within a unique matrix of thick mica with a strong yellowish tint

From the Upper Ordovician Period - Ashgill Stage - Ktaoua Formation

Measurement is of box

It is found in many sites across the world

These specimens of Mosasaur (Mosasaurus anceps) teeth are embedded in matrix

with color intensity usually deepest at the termination or tip of each crystal

Paradoxides sp

This preglabellar ring (head shield) is covered in many sensory pits which may have held hairlike features when the trilobite was alive