We love geodes, and it’s easy to see why. They’re nature’s mystery boxes; when you break one open, you get to be the first person ever to see what’s inside. This article will discuss different types of geodes with pictures.
What Type Of Rock Is A Geode?
Geodes are hollow rocks filled with crystals and other cool minerals. No two are exactly alike, and unique varieties can be found depending on where you look.
Different Types Of Geodes With Pictures
We will check out some of the most amazing geodes worldwide.
The U.S. has its very own geode hotbed, and it’s centered in the town of Keokuk, Iowa. The geodes are so plentiful here that they can be found decorating yards, lining flower beds, and even being used as door stops. And they can be big. One reported find was over 27 inches across and nearly 500 pounds.
The geode riches are due to a huge body of dolomite and limestone known as the Warsaw Formation that formed about 350 million years ago and stretched through parts of Iowa, Illinois, and Missouri.
Here, geode hunters often find them exposed along banks and cliffs of rivers and streams. Most of these geodes are of the classic variety, chalcedony shells filled with quartz crystals, but some very interesting variations can also be found.
Snowballs contain globes of smooth white chalcedony that appear to sparkle with frost. They’re found on the Illinois side of the formation. You may also find wisps of milorite, a metallic mineral that grows in a fine hair-like crystal habit.
Barite rosettes, also known as desert roses, are curious features you may find in the geodes from Illinois’s evocatively named Crystal Glen Creek.
Geodes from the Missouri side also have plenty to offer, including calcite crystals that are pretty in pink. In Alexandria, you can even find geodes lined with miniature octahedrons of golden pyrite.
Las Hoyas Geodes
With everything from sphalerite crystals to blades of selenite and even bubbly growths of bright green malachite, Warsaw geodes can really keep you guessing.
But it can’t match the production of Las Hoyas in Chihuahua, Mexico, where many thousands of pounds of geodes are mined daily.
They are found a hundred feet underground, where miners drill elaborate tunnels and separate them from thick rock walls using pickaxes. The surveyors have developed a feel for judging how hollow each geode is simply by balancing it in their hands, but what’s inside remains a mystery until it’s opened.
You may find colorless or smoky quartz, or you could see pillowy walls of blue-gray calretinin or dog-tooth-shaped crystals of calcite. Inclusions of many dozens of different minerals are possible, including citaray apatite and hematite.
One of the most unique is mordenite, a spongy white mineral that fills the cavity with its own cotton stuffing, kind of like an ancient Build-A-Bear. The beauty of Las Hoyas geodes is world-renowned and has turned this two-mile stretch of remote desert into a multi-million dollar enterprise.
But are they the most impressive?
The amethyst cathedrals of Brazil may have something to say about that. Approximately 125 million years ago, one of the largest discharges of lava ever on earth resulted in the Piranha Flood Basalt Province, where today a multitude of huge amethyst geodes can be found.
The heaviest concentration is found in the aptly named town of Amatista do Sul. They have been mining geodes here since the 1800s. When the miners hit a pocket, they use a small light to peer inside.
Geodes are so plentiful here that if the crystals aren’t colorful enough, they’ll just continue to blast through the rock. But when they do find a richly colored geode, out comes the hammer and chisel.
Miners will work for as long as a week to carefully separate these specimens from the host rock. These amethyst cathedrals can be over 30 feet long and encased in a thin green layer of celadonite. Many will later be heated to produce the beautiful yellow-orange of citrine. Having one of these in your gem collection should do the trick if you want to draw eyeballs. But size isn’t everything.
Further north in the state of Paris or Brazil, you can find an entirely different kind of geode that’s equally unforgettable. In fact, these may be the strangest we’ve ever seen, called polyhedroids.
These geodes aren’t round but are instead made up of flat faces that intersect at varying angles. They have a geometric look, but they’re never symmetrical.
One theory suggests these originally formed within a lattice between plates of other minerals that later weathered away. Most are hollow and may reveal colorless quartz crystals or multi-toned agate when cut open. Some of the most prized specimens feature alternating bands of agate and crystals.
Normally, geodes truly embody that old adage, “it’s what’s inside that counts.” But that’s not the case for the geodesic fossils of Brown County, Indiana.
Despite their sparkling quartz interiors, many remain unopened because what collectors really go for are the exterior shapes of strange calyxes and columns.
These geodes are the fossilized remains of ancient sea critters like gastropods, brachiopods, crinoids, and even coral. It’s thought that their shells and skeletons served as seeds for gypsum deposits, which were later replaced by quartz and calcite.
Agatized Coral Geodes
Sea life is also responsible for the striking agonized corals of Tampa Bay. A giant undersea reef died here about 20 million years ago, and its calcium carbonate was eventually replaced with calcitonin.
The rich diversity of minerals resulted in geodes with brightly colored agate interiors. The warm shades of carnelian and sard are offset with yellows, blues, and ivory. Tunnels made by burrowing clams and seaworms create interesting interiors.
The geodes themselves may be shaped like fans, fingers, or even hourglasses. Though original finds were concentrated near Tampa, these have also been found along many other Florida beaches. At low tide, intrepid geode hunters use a pry bar to feel for them in the clay beneath the sand. Many of the geodes found here will also be in hydros.
Enhydrous is a special geode variety that contains trapped water. Ideally, this water is found behind a translucent agate that can be polished to such a thinness as to make a window through which the water’s movement can be seen. Watching this can be totally addictive. They are found in many different locales, often near beaches.
A more obscure and rather scary variety of liquid-bearing geodes are those of Napa County, California’s now-defunct Pioneer Mine, which were reported to contain mercury.
We can’t end a post about different types of geodes without mentioning one that many tout as the largest. The Crystal Cave at Puddin Bay, Ohio, is 30 feet deep and lined with massive tabular celestine crystals, a strontium sulfate. While Spain’s selenite-covered pulpy geode covers more ground,
Crystal cave fans argue their spot is shaped more like a traditional geode. Maybe they’re both pretty epic. While Ohio contains some of the largest deposits of celestine in the world, Madagascar produces the bulk of celestine geodes, many filled with large, well-formed crystals of a lovely sky blue.
Conclusion On different types of geodes with pictures
There are so many cool geodes in the world, and we’ve only scratched the surface. The post on different types of geodes with pictures provides a fascinating glimpse into geology and mineralogy. Geodes are natural rock formations filled with crystals, minerals, and other geological wonders, making them a sought-after item for collectors and enthusiasts alike. Hope this article can help you.
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