Agate

Agates form in rock cavities
As rock cavities are primarily bubble rooms in volcanic rocks, here the bubbles contained in the outflowing lava came into contact
Gases did not reach the surface of the lava flow and could not escape. Instead, they were trapped in the cooling lava and formed a cavity in it, which in a later process filled with agate, quartz, calcite or other mineral substances. Volcanic rocks include both basic volcanites, such as basalt, and acidic volcanites, such as rhyolite.

There is a great variety of agates
Eye agate, banded agate, dendrite agate, star agate, water agate, fortress agate, fire agate, flame agate, crazy lace agate, landscape agate, snake agate, rubble agate, etc. etc.

mineral class
Agate belongs to the quartz group and to the mineral class of the oxide formula: SiO2 (quartz) + Al, Ca,Fe,Mg,Mn.

Mohs hardness: 7
density: 2.6
fissility: none
Transparency: translucent