Egg Stone Agates Information

Egg Stone

• Egg stone, also called "thunder egg" by American Indians, is a type of agate geode which can be found in large amounts in Jefferson County, Oregon, according to Minerals.net. Egg stone is the state rock of Oregon.

Geode

• A geode is a semispherical limestone rock node or shell, also known as a "vug," enclosing an agate interior, according to Agate Geode.com. Agate geodes can form in lava beds, often occurring within hardened volcanic gas bubbles in the rock.

Appearance

• The outer appearance of an egg stone agate is rough, rather nubby rock. The interior of the geode, however, is usually very beautiful---an open cavern lined with banded agate and sometimes crystals; color can vary considerably.

Size

• An egg stone agate can range from the size of an olive pit to almost any size. A large agate geode was mined in Brazil that weighed nearly two tons. Most egg stone agates are within an inch to five inches in diameter and roughly spherical.

Agates

• The name "agate" was taken from the Achates River in Sicily (now the river Drillo), where deposits of agate and chalcedony, mined by ancient Greeks and Romans, are still found, according to Agates.org. Agates are found in nodular or clumpy masses, often in volcanic lava rocks, where they form in concentric layers or bands and fill cavities in the rock.

Varieties

• Agate occurs in a wide variety of colors and patterns, according to Minerals.net. In addition to egg stone agate, varieties include moss agate, dendritic agate, fire agate and blue lace agate.