Agate

Agate is varied and beautiful. There are several types of agate:
Cyclops agate is a Mexican agate showing only a single eye.
Moss agate has colors and filaments suggestive of vegetable growth.
Dendritic agates have fern like patterns in them.
Turritella agate is formed from silicified fossil Turritella (snail) shells.
Agatized coral is in essence petrified cora often referred to as Petoskey stone.
Certain stones when viewed in thin sections using transmitted light show a lovely diffraction spectrum caused by the extreme delicacy of the successive bands. They are called rainbow agates. Sometimes agate coexists with layers of masses of opal, jasper or crystalline quartz.
Other forms of agate include carnelian agate, faceted Botswana agate, Greek agate, Brazilian agate, Ellensburg blue agate, blue lace agate, plume agates, Mexican crazy-lace agate, and much more.
You’ll find agate used in pins, brooches, paper knives, inkstands, marbles and seals. Agate is also used to make mortars and pestles used by pharmacists to crush and mix chemicals. It is also used for leather burnishing tools.