Agate Quartz

Quartz is silicon dioxide, SiO₂. Quartz is abundant in the Earth's crust, being the chemically simplest form of the silicates. All the samples here are displayed in the Smithsonian Museum of Natural History. The appearance of agate is strikingly different from our visualization of quartz as clear crystalline material! The layered structures of agate record a crystal growth process which produces dramatic patterns. The sample at right is about 4x5 cm and is from Chihuahua, Mexico.

Microcrystalline quartz rocks are collectively called chert, but varieties of chert are given other specific names. Agate is one of the distinctive varieties of quartz.

This specimen of agate is about 10x10 cm and is from Chihuahua, Mexico.

This specimen of agate is about 13x13 cm and is from Chihuahua, Mexico.

This specimen of agate is about 15x15 cm and is from Dryhead, Montana.

This specimen of agate is about 5x4 cm and is from Coyamito Rancy,Chihuahua, Mexico.