Geodes and Amethyst Caves

Nodules are roughly sphere-shaped rocks. Those which are at least partly hollow are called geodes. The cavities are formed when volcanic rocks have large steam bubbles inside them. Over time, crystals may form lining the inside walls of the cavities.

The most common material found in the cavities of geodes is quartz. The cavity in most geodes is surrounded by a layer of agate in colored bands which gives a spectacular effect when polished.

If the quartz is deposited slowly with relatively few impurities, it will line the cavity with sparkling crystals. If the quartz is deposited rapidly, the cavity will be filled with varicolored bands of agate, which is an extremely fine grained form of quartz.

Quartz Geode Agate geode

The crystals which form in geodes may be any color. The most common are white, smoky, gray, lavender and brown. Among the most spectacular are those with purple amethyst crystals.

Geodes occur in relatively few places in the world but, in these places, they are abundant. They are found in the Mississippi and Ohio river valleys in the USA and the Chihuahua area of Mexico. The main source for amethyst geodes is the Rio Grande du Sol region in Brazil and the adjoining part of Uruguay. Huge geodes, described as amethyst caves and cathedrals, have bee found in Brazil. The largest are up to 10 meters tall.

Amethyst Cave Amethyst cathedral

Geodes now available (at eBay):

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Super Purple Amethyst Geode Cathedral URUGUAY Free Standing 113mm 4.5" 3657rxx

AU $89.46
End Date: Saturday Sep-12-2020 4:05:25 EST
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Purple Amethyst Geode Cathedral Cluster URUGUAY 3.2" Free Standing 80mm 3659rxx

AU $103.38
End Date: Saturday Sep-12-2020 4:03:31 EST
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Super Purple Amethyst Geode Cathedral URUGUAY Free Standing 158mm 6.2" 3685rxx

AU $145.15
End Date: Saturday Sep-12-2020 2:34:16 EST
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Purple Amethyst Geode Cathedral Cluster URUGUAY 3.5" Free Standing 88mm 3655dxx

AU $103.71
End Date: Saturday Sep-12-2020 2:34:14 EST
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3654dx Purple Amethyst Geode Cathedral Cluster URUGUAY 3.8" Free Standing 98mm

AU $90.49
End Date: Saturday Sep-12-2020 2:17:19 EST
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Super Purple Amethyst Geode Cathedral URUGUAY Free Standing 117mm 4.6" 3686rxx

AU $89.46
End Date: Friday Sep-11-2020 17:54:18 EST
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Super Purple Amethyst Geode Cathedral URUGUAY Free Standing 138mm 5.4" 8354fxx

AU $103.80
End Date: Friday Sep-11-2020 16:49:06 EST
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