Agate Geode - Mineral and Healing Properties

Chemistry: SiO4 silicon oxygen tetrahedra

Class: Silicates

Subclass: Tectosilicates

Uses: Mineral specimen and ornamental uses

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  • Keokuk Geode
  • Agate Geode
  • Agate Geode


Geodes are rock and crystalline formations found in volcanic and sedimentary rock. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Other geodes are completely filled with crystal, being solid all the way through. These types of geodes are called nodules.

These formations are common in just a few states in America, but can be found anywhere from store shelves, where they are sold as paper weights, to lawn ornamentation in landscaping.

Origin Of The Name

The name Geode" was derived from the Greek word "geodes," meaning "earth-like".

Interesting Facts

A geode begins as a bubble in volcanic rock or a hollow in sedimentary rock. The outer shell of the bubble or hollow will eventually harden, and water forms on the inside of the cavity. The water contains silica precipitation that contains a variety of dissolved minerals.

These hollows remain full with mineral rich water or get filled again if the water table rises. This water then with the constant drying out then re-depositing of mineral water forms the crystalline structures over a very long period of time. Another way these crystals form is through a leaching process. As the mineral rich ground water permeates the hollow, it begins to form the chalcedony shell through silica deposits. After continual permeation the remaining deposits eventually form hexagons shaped crystals and entirely fill the hollow if allowed to grow. On occasion some geodes that are completely filled have an inner layer of agate surrounded by the hexagon crystals. This is thought caused by a silica gel that got through the chalcedony and later dried.

Where Is It Found

Keokuk, Iowa is known as "the geode capital of the world" for very good reason. A virtually countless number of geodes has been collected from the Keokuk area over especially the last 150 years.

Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term "vug" is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American Midwest, rounded cavities in sedimentary formations. After rock around the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface. Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber. Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.

Geodes are common in some formations in the United States (mainly in Indiana, Iowa, Missouri, Kentucky, and Utah). They also are common in Brazil, Namibia, and Mexico. A large geode was discovered in Put-in-Bay, Ohio in the early 20th century. It is known as Crystal Cave, and tours are possible during the summer. In 1967, Iowa designated the geode as the official state rock, and it has a Geode State Park.

What Do We Do With It

Small to medium geodes make for useful paperweights in an office or on a home desk. Medium to large geodes make sturdy bookends for an office or a home library. Geodes of any size can be split open and polished to produce a one-of-a-kind bowl or dish to house various household objects. Large geodes make for beautiful and interesting glass-top coffee or end tables.

Metaphysical Uses

Agate's most noticeable properties overall are balancing yin/yang energy, courage, protection, healing, and calming. Historically it was placed in water for cooking or drinking to dispel sickness. The Metaphysical and Healing Properties Lore of any specific type of agate depend to some extent on the color of the agate, but all agates have certain things in common.

Agate is a stone of strength. It was used by the Ancients on the breastplates of armor to give warriors strength and make them victorious in battle. Energetically, it is considered to give strength in both battle and physically.

Agate enhances creativity and strengthens the intellect, making it a beneficial stone for both students and artists. It is also known as a good luck stone. As a stone of harmony, one of the things agate does is balance yin/yang energy. Agate increases energy. However, because it is a grounding stone, it does not increase energy at all times, but rather enables bursts of energy as needed. In this way, agate is a conservation stone, and enhances longevity.

Agate is a very protective stone. It is especially protective for children, and makes an excellent stone for children's amulets, medicine bags, jewelry, or just to carry around in a pocket. Agates are said to be especially useful for protecting children from falling.

Emotionally, agate gives courage, emotional strength, self-confidence, and dispels fears. It can also lessen feelings of envy by grounding the emotions. In the same way, it assists with acceptance of all things. It can be very beneficial for self-examination as well as examination of the circumstances one finds oneself in. These qualities make agate superior for easing anxiety and stress. Plume agates are especially helpful for anxiety and stress relief. Particularly when placed on the Solar Plexus (3rd) Chakra it can help one to accept one's emotions, thereby helping overcome those emotions that one wants to remove.

Physical Characteristics

Color: Clear quartz is by far the most common color of Keokuk Geodes.

Luster: Glassy to vitreous as crystals, while cryptocrystalline forms are usually waxy to dull but can be vitreous.

Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque.

Crystal System: Trigonal; 3 2

Crystal Habits: Widely variable but the most common habit is hexagonal prisms terminated with a six sided pyramid (actually two rhombohedrons). Three of the six sides of the pyramid may dominate causing the pyramid to be or look three sided. Left and right handed crystals are possible and identifiable only if minor trigonal pyramidal faces are present.

Cleavage: Very weak in three directions (rhombohedral)

Fracture: Conchoidal

Hardness: 7

Specific Gravity: 2.65

Streak: White

Associated Minerals: Numerous and varied but here are some of the more classic associations of quartz (although any list of associated minerals of quartz is only a partial list): amazonite a variety of microcline, tourmalines especially elbaite, wolframite, pyrite, rutile, zeolites, fluorite, calcite, gold, muscovite, topaz, beryl, hematite and spodumene.

Best Field Indicators: First the fact that it is very common (always assume transparent clear crystals may be quartz), crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage.

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