Meriden Mineral Club
Mineral Forms
Forms are a third category that guide collectors on their selection of minerals. The following are examples of mineral forms with "weird" designs:
Geode
This is an fine example of a classic 5" geode (half). They are officially called Los Choyas geodes and are from Chihuahua, Mexico. They are recognized as the best representative of the geode form. Most of them have clear quartz crystals in the hole. but sometimes they are filled with amethyst or smoky quartz. The better collector specimens are rim polished and look great.
Botryoidal
This is a fine example of the Botryoidal form. Botryoidal is derived form the Greek word meaning grape like. The base mineral is Prehnite and is found in the trap rocks of New Jersey, Connecticut and Massachusetts. As you can see it's a very pleasing mineral.
Carlsbad Twin
Carlsbad Feldspar Twin Intergrown Crystals. If we take a standard feldspar crystal, saw it in half, take one half and turn it around and then fuse(merge) it into the other, we have this shape. Courtesy of nature. It is quite amazing! This sample comes from Colorado.
Botryoidal
The form is Botryoidal aggregate. The mineral is Goethite. Both the shape and the absolute coal black color are appealing. It's really a very neat specimen!
"Iron Cross" Twin
An "Iron Cross" Pyrite twin crystal from Columbia. These are two intergrown pentagonal dodecahedrons (also known as "pyritohedrons"). This is an amazing crystal structure. Also, it just looks great in a collection or on your coffee table!
"Micro" Botryoidal
This is a good example of Grape Agate from Indonesia. The mineral experts have deterrmined that the sphericals are too small to be called "Botryoidal" so I call it Micro-Botryoidal, but offically the term is "globular". Either way it is truely an amazing specimen
