this year’s WSMGS show theme is Wyoming's minerals.

When discussing minerals, rockhounds often think of images of exquisite crystals. There are however, an incredible variety of minerals that come in a myriad of sizes, habits, colors and lusters. 

Minerals can have cryptocrystalline to massive crystals. Many expect minerals to have a glossy shine, but they can look earthy, dull and sometimes even brilliant (like a diamond). 

Wyoming boasts many minerals, some stunning, some plain, some unusual, and some uncommon or rare, but all of them fascinating.

Rockhounds often use terms like rock and mineral interchangeably. Some would consider a piece of jasper or agate a rock because it is not crystalline.

Geologists see the issue differently. So, what exactly is a mineral?

As defined by the USGS: “A mineral is a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties.” 

“Common minerals include quartz, feldspar, mica, amphibole, olivine, and calcite.” 

(https://www.usgs.gov/faqs/what-difference-between-rock-and-mineral).

In the same article, the USGS defines a rock as: “an aggregate of one or more minerals, or a body of undifferentiated mineral matter. 

“Common rocks include granite, basalt, limestone, and sandstone.

“Sedimentary, metamorphic or igneous rocks are made up of one or more minerals. Some igneous rocks like obsidian are amorphous compounds that lack internal structure.” 

Jet, amber, gilsonite and other organic compounds aren't considered minerals. Mineral shops and collectors often call these compounds minerals which would drive a geologist crazy.

Opal too is an amorphous compound that lacks internal structure but is often grouped with silica-rich minerals. 

Most rockhounds have more minerals in their collections than they realize. Many specimens referred to as “rocks” are minerals. 

Is agate a mineral? Short answer is, yes. It is a variety of quartz. Likewise chalcedony, jasper, citrine, amethyst, rose quartz, milky quartz; smoky quartz, and the list goes on are all varieties of quartz and should be labeled that way. (See the Quartz Page for a list of quartz varieties http://www.quartzpage.de/ovr_text.html.)

How about Wyoming Jade? Is it a mineral? No, it's actually a metamorphic rock type, nephrite, which is composed of microscopic crystal fibers of amphibole in the actinolite-tremolite mineral series along with trace to small amounts of other minerals. There is no mineral called jade. That is a gem and lapidary term. 

Wayne Sutherland in his new book Wyoming Jade states: “Because true nephrite is composed of one mineral series, it is often described as though it was a mineral”. 

Nephrite has physical properties that are similar from one specimen to the next. Good quality specimens are largely microcrystalline amphiboles.

Since the impurities are hard to see, good quality specimens could be classified as a mineral.

Is Trona a mineral? Yes, is a non-marine evaporite mineral which is common in southwestern Wyoming. Other rare minerals like Eitelite, Thermonatrite, Shortite are found with it in the State’s mines.

Is Bentonite a mineral? No, it is a mixture of clay minerals formed by the alteration of volcanic ash in a marine environment and would be considered a rock.

Clay minerals themselves are not what most rockhounds think of when someone says mineral. They have very small crystals that are earthy and dull. They look like dirt but are minerals. Clays cannot often be distinguished from each other without laboratory methods so most rockhounds would group them as “clay minerals” or “clay.” 

A group of minerals is two or more mineral species having identical or closely related structures and chemical compositions. 

Many minerals belong to groups with names familiar to the rockhound, though the individual mineral species in that group mostly likely have unfamiliar names. 

One such group is Garnets. Most rockhounds know that name but are unfamiliar with the group members’ names: almandine, pyrope, spessartine, uvarovite, grossularite, andradite. 

This is often the case with other groups of minerals such as feldspars, amphiboles, micas, pyroxenes. 

Sometimes these groups have varied chemical compositions in between “end members”. Laboratory methods are often required to identify the minerals species.

If the specific mineral species is not known or unable to be determined with available tools, the rockhound or geologist may call a particular specimen by the group name (ie: an amphibole or a feldspar). 

Discovering the minerals of Wyoming can be a lifelong adventure. There always seems to be something new and interesting.

Come to this year’s Wyoming State Mineral and Gem show and discover some interesting minerals from Wyoming and around the world.

The following list, while not exhaustive, features both common, uncommon and rare Wyoming minerals. Have fun discovering Wyoming minerals. https://bighornbasinrockshow.com/wyoming-minerals-1