This large calcite crystal formation is housed within some beautiful andesite breccia.  The variety of patterns and colors helps form an amazing specimen where you can find something new almost every time you look at it.

Rock type: Calcite

Calcite is a very common mineral found all over the world.  It is the main component of limestone and marble and can be found in all rock types (igneous, sedimentary and metamorphic.  It can be distinguished from quartz by its hardness (Mohs hardness 3), its crystal structure (calcite form rhombohedral or prismatic crystals), its fracture (calcite fractures along 3 planes resulting in smooth surface that form rhombic shapes, its reactivity to dilute acid (calcite will bubble when exposed to dilute acids like hydrochloric acid).

Chemical composition: CaCO3