What do amethyst geodes look like

As geodes get larger you can get more variability in the shape. While they may be more elongated or complicated in shape, they will still be rounded and lacking any sharp or angular features. Geodes are actually pretty ugly rocks! But as we all know, real beauty is on the inside. Sometimes if you look close you may be able to spot little veins of the crystal inside showing through to the exterior, but overall a geode will look very bland and even ugly.

Tip: Geodes tend to be fairly ugly rocks at first glance. The exterior of a geode tends to be well-weathered and pockmarked. The bumps will be fairly large. They should help make identifying a potential geode a lot easier once you know what to look for. One dead giveaway of a geode is if it makes any noise when you shake it. Jiggle your rock around close to your ear and listen for any movement inside.

That sound is a sure sign that there is empty space within the rock for material to move around in. Tip: Shake a potential geode and listen for movement inside. Chalcedony crystals as so small that they cannot be seen with the unaided eye. In a geode, a tiny crystal of chalcedony will attach to the wall and it will be coated with a layer of tiny chalcedony crystals all pointing outwards from the seed crystal.

Layer after layer is deposited, and the early result looks like a small hemisphere attached to the inner surface of the geode. These tiny hemispheres begin to grow into and over one another, and the result is a landscape that looks like a pile of grapes.

This hemispherical geometry is a common crystal habit of chalcedony known as botryoidal. An example of a geode lined with botryoidal chalcedony is shown in the accompanying photo.

Fake geode: Photo of a galena-lined "geode" made from pottery clay decorated with paint and a covering of fine galena crystals.

Purchased in Marrakesh, Morocco. As with most popular or valuable objects, fake "geodes" have been manufactured by people and offered for sale as naturally-formed objects. If you are a collector paying serious money for a spectacular geode, you need to know enough about geodes and the mineral materials that occur in them to spot a fake. Expert gemologists, mineral collectors, paleontologists and others who buy expensive specimens are regularly fooled by fakes.

The accompanying photo shows a fake geode bought in Marrakesh, Morocco. It was being offered as a galena-filled geode. However, the body of the geode was made from a pottery material with a coating of fine galena crystals glued on to simulate a druse. Many highly skilled artists in Morocco make a living producing imitation mineral and fossil specimens.

Oregon Thundereggs: Examples of thundereggs sawn to display their interior. The top two are halves of a single egg about three inches in diameter.

It is filled with gray chalcedony with gray agate and drusy quartz in the center. The bottom is a half egg about six inches in diameter with gray banded agate around the outside, white agate towards the center, and a drusy quartz cavity in the center.

Learn more about Oregon gemstones here. Herkimer diamond in a vug: A vug is an unlined cavity that will not remain when the rock that contains it weathers away. The rock in the photo is about 18 centimeters across. Geodes, nodules, vugs, concretions and thundereggs are all sites in the earth where substances dissolved in subsurface waters precipitate to form crystals or rounded objects.

These objects share many common features and form by similar processes. They all also produce objects that attract attention and stimulate debate. These objects are often confused with one another, and their names are used incorrectly because the speaker misunderstands the words or interprets the object incorrectly. They are also used in different ways by different people in various parts of the world.

Who is right and who is wrong? Some generalizations drawn from the common usage of these words are offered below A few areas in the United States are well-known for their geodes and geode-like objects. Geodes are so popular in a few states that they have achieved the status of "official state rock" or "official state gem. The Oregon Senate designated the Thunderegg as the official "state rock" in And, the Minnesota Legislature designated the Lake Superior agate as the official state gem in Some of the more noteworthy localities are described below.

There are many more, and a good place to read about some of them is in a book titled Geodes: Nature's Treasures by Brad L. Cross and June Culp Zeitner. Keokuk geode from Lee County, Iowa. One of the best-known occurrences of geodes in the world is an area surrounding the community of Keokuk, Iowa.

It is located near the three-state intersection of Illinois, Iowa and Missouri, with geodes of this locality being found in all three states. The geodes formed in the limestones and dolomites of the Mississippian-age Warsaw Formation. Most of these geodes are a few centimeters across and have outer layers of white to gray to blue-gray chalcedony with interiors lined by tiny quartz crystals.

Most of the geodes found here have weathered free of their carbonate host rock and are now in the local soils and stream sediments. A few of these geodes contain interesting crystals of ankerite, aragonite, calcite, dolomite, goethite, gypsum , kaolinite, marcasite , millerite, pyrite , sphalerite and other minerals.

A few have been found with liquid petroleum inside. These tumbled stones show some nice agate banding and often a crystalline quartz core.

Specimens and photo by RockTumbler. The Lake Superior agate is a fortification agate that fills cavities in basalt flows that formed over a billion years ago in the Lake Superior region.

Over time, silica-rich groundwaters filled these cavities with agate and crystalline quartz. Most of them have been completely infilled and are more properly called a "nodule. The agate within them is typically reddish brown, red, and orangish red in color. These colors are caused by trace amounts of iron that was incorporated in the agate.

Kentucky geode with millerite. These have weathered out of their host rock units and are now found in stream valleys. Other areas where numerous geodes are found in Kentucky stream valleys include the Green River in the south-central part of the state and along ancient terraces of the Kentucky River.

The Geological and Natural History Survey of Wisconsin reports numerous occurrences of geodes, Lake Superior agate nodules, and thundereggs within the state. Croix, Sheboygan, Trempealeau, and Washburn Counties. Fluorescent Dugway Geode: Many Dugway geodes contain fluorescent minerals and produce a spectacular display under UV light!

Specimen and photos by SpiritRock Shop. Between 32, and 14, years ago, Lake Bonneville covered much of what is now western Utah. Wave action along the shores of the lake eroded geode-bearing rhyolite flows. The wave action, along with weathering, liberated the geodes from the rhyolite and deposited them several miles away in lake sediments of what is now known as the Dugway Geode Beds.

When broken or cut open, geodes reveal a lining of crystals or other materials inside. Many of these crystals can be quite beautiful, such as the purple quartz known as amethyst. Some geodes even contain liquid petroleum. Calcite geodes contain white crystals, but sometimes these can be other colors, and under fluorescent light additional colors show up.

Other examples of geode interiors include celestite, agate, smoky quartz and rose quartz. Chalcedony is a common mineral coating for many geodes, and it is permeable to water over time. Anhydrite geodes have interiors that resemble cauliflower. Other examples of minerals found in geodes include:. A nodule rock is a solid rock with no hollow center.

So unlike geodes, the interior of a nodule rock contains no empty space. It does, however, contain minerals. Nodule rocks are harder than the rocks that surround them.

They can be found in sandstone, shale or limestone. Some nodules contain iron. Pyrite nodules contain pyrite crystals. Others contain crystals or fossilized remains, even though their insides are not hollow. A quartz nodule, for example, contains an interior of quartz. Nodules can be concretions, which can reach many feet in diameter. These tend to be found alongside areas of erosion. First, there's the formation of the cavity and then the formation of the crystals. An amethyst geode is a hollow rock with amethyst crystals lining the inner walls, so first the cavity must be formed.

This can happen anywhere there is or was lava close to the earth's surface. As a result, amethyst geodes can be found in thousands of places around the globe. The first step in the natural process that creates amethyst geodes is the formation of gas cavities in lava. The gas cavities can form from bubbles just like the carbonation causes bubbles in your soda. Some scientists theorize that the cavities can also be formed when cooling lava flows near tree roots or other things sticking out of the ground.

The cooling lava hardens completely before filling in around the outcrop, creating a cavity. The cavities then fill up with a silica-rich liquid that contains trace amounts of iron.