Tag Archives: Wyoming

Green Rocks and Minerals

This past fall, I was working on a gold project near Cheyenne, Wyoming and met two old friends for dinner. One had an affection for green minerals and rocks, so I thought I would tell you a little about some green rocks in my back yard.  One specimen has a lot of lumps and kind of reminds me of brains. So I call it jaded brains. It has a pleasing light-green color and was picked up in the jade fields of Wyoming.

Light green jade

The geological and geochemical processes that produced jade are intriguing. The jade fluids produced under great pressure (and temperature) tended to replace much of the original rocks and minerals to produce jade. Each atom of the original mineral or rock was mobilized and replaced by the atoms that make up jade. We don’t know if this was a rapid process or a process that took place over millions of years.  But we can see the results and sometimes, much of the original rock matrix was replaced by jade leaving feldspar phenocrysts (larger crystals in a fine-grain groundmass or matrix) somewhat in tact.  In other specimens, we find quartz crystals that are preserved and untouched, but in others, even the quartz is not safe, as we find evidence of quartz (hexagonal) being replaced by jade.

Jade porphyry. Much of the original rock matrix was replaced by jade leaving some greenish
white feldspar in place that are also partially replaced.

Jade specimen with quartz crystal preserved.

GOLD & OTHER PRECIOUS METALS

Little was known about gold in Wyoming, thus I set out to map, evaluate & find more. I discovered gold everywhere I looked. I was amazed at how much had been overlooked. I published compendiums that are used by prospectors & geologists & mapped several mining districts that were previously unmapped or only partially mapped. I even found a previously unrecognized ultramafic massif with significant palladium, nickel gold & copper mineralization & a whole new district.

I have many great stories & memories about discoveries & prospectors I met. Hopefully, I will be able to find time to write a book about these, as such stories should be preserved. There are stories about hundreds of nuggets in ball jars in Shorty Haddenham’s trailer at Atlantic City, dozens of nuggets found by a Ft. Collins prospector, a prospector who spent one entire winter jumping a claim & panning out barrels of mica thinking he had found the Mother Lode & my research along the UP corridor- we found gold everywhere including the Laramie City dump.

Gold photos below – 34 oz nugget (Rock Creek, South Pass), gold from Douglas Creek, and gold from Dickie Springs (South Pass).

I mapped the South Pass greenstone belt at the southern tip of the Wind River Mountains which included several historic gold districts: Lewiston, South Pass, Atlantic City, Miners Delight & others. I identified several hundred gold anomalies & found gold was structurally controlled in reef ore shoots that are very rich down plunge. One deposit I mapped (Carissa) is a major deposit 1000 ft wide, 1200 ft long & probably continuous a few thousand feet downdip. This deposit was withdrawn by the legislature without any scientific review – such abuse of political power literally took away a mountain of gold & many good jobs.

Geology led me to many discoveries. The Rattlesnake Hills were an obvious target, so in 1981, armed with the concept that the RH were part of a fractured greenstone belt intruded by Tertiary alkalic volcanic rocks, I knew there had to be gold. And I found gold in the RH in veins, shears, Tertiary breccias, stockworks, pyrite. I also found significant gold elsewhere in Wyoming – Seminoe Mountains, Mineral Hill, Purgatory Gulch, more.

Left – Gold at the end of the rainbow at the Duncan mine, & view of part of the auriferous shear at the Carissa – a major gold deposit with potentially >US$billion in gold.

HEY, there are several other (Older Posts) – be sure to check them out by clicking on Older Posts below

OTHER GEMS

During 30 years at the WGS, I found hundreds of deposits. How did I do this? I used geology as a guide; I looked at things differently and was motivated to look and search for mineral deposits.

While conducting reconnaissance, I discovered jasper in several old mines at Tin Cup, in an outcrop near the south edge of the Rattlesnake Hills, and found jasperoid at Quaking Asp Mountain. Some of the Tin Cup jasper is extraordinary and found in masses weighing several hundred pounds. The jasper in the Rattlesnake Hills contained some fossil leaf imprints.

Nearly everywhere I explored, I followed trends and examined geology which lead me to other mineral deposits. I was curious enough to find out what some of the unusual minerals were that I picked up, and as a result, I identified more than a dozen minerals that had never been reported in Wyoming.
Above – barite from Mine Hills, Shirley Basin. Middle- a group of cabochons cut from various material. Below – beautiful jasper from Tin Cup & me standing in old prospect pit. These prospects were reported as having high-grade gold values. I found no gold & likely these were left over from various gold mining frauds and scams from the 1800s. Note the large mass of jasper to my right (probably a few tons of high quality material).


Left – Labradorite feldspar collected by Norma Beers in the road bed of Albany County 12 in Albany County. This is just one of millions of gem-quality feldspar found in this area – yet this resource remains unexplored.

OPAL

A rockhound from Riverton mentioned opal south of town. The Cedar Ridge deposit lies along the highway & is cut by numerous oil field roads, no one had recognized that this place had one of the largest opal deposits on earth! A few old geological reports from 50 years ago briefly mentioned opal, so I was surprised to find opal scattered over 14 mi2, opal masses >79,000 cts along the edge of the road & common, fire & precious opal with scattered Sweetwater agate & some of the nicest decorative stone on earth. All within Tertiary age volcaniclastic sedimentary rocks that had a notable contribution of volcanic ash erupted from Yellowstone in the geological past.

This gave me a clue – nearly all of Wyoming was blanketed by volcanic ash (as was Nebraska and South Dakota). Guess what? There are other opal fields waiting to be discovered. So I found millions of carats of common & fire opal & traces of precious opal (including black opal) that suggest as soon as someone digs, valuable veins of precious opal will be found as depth!
Photos show precious opal, Sweetwater agate, cobbles of opal in oil field adjacent to road. Below are fire and common opal

PERIDOT

In 1997, I decided to search the Leucite Hills in western Wyoming for diamonds (see photo at left). I didn’t find diamonds, but mark my words – “DIAMONDS WILL BE FOUND HERE”. This is an easy prediction to make based on geology.

The Leucite Hills consist of several lamproite volcanoes & flows that erupted 900,000 to 3.1 million years ago. They started their journey under one of the thickest parts of the Wyoming Craton. Cratons are very old, cool, continental cores necessary to have melting deep within the earth’s upper mantle (where diamonds are formed). While exploring this region, I collected grab samples from lamproite in the northeastern part of the field & two yielded chromites with similar geochemistry to chromites found as mineral inclusions in diamond – thus this tells me some of the volcanoes began their journey at 90 to 120 miles beneath the surface where diamonds are common.

Diamondiferous lamproites are found at Murfreesburo, Arkansas; Argyle & Ellendale, Australia; Majhgwan-Chelima, India; Kapamba, Zambia; Aldan, Russia & Bobi, Ivory Coast. The richest deposits are typically found in olivine lamproites which often alter to serpentinite (a very soft material) that erodes quickly, thus such deposits are usually hidden within a field of leucite lamproites (which are much harder rock). Thus, this all suggests a few diamonds are likely to occur in the lamproites with diamond-stability chromites, but the locations for rich diamond deposits are hidden. Along the northern edge of this field, a large sand dune field that marks the location of a major continental shear – a favorable structure for hidden lamproites. One can almost guarantee there are diamondiferous olivine lamproites in this area hidden under a few feet of sand. Lamproites are also well known for colored stones – brown, yellow & the beautiful, extremely rare Argyle ‘Pinks’. Some have sold for >$US1 million/carat!

While searching for diamonds, I started looking for olivine. In 1997, I came across two green anthills at Black Rock – the ants had collected all of the available olivine in the immediate area & decorated their hills. So I collected the hills & processed them for diamonds – but all we found were 13,000 carats of flawless peridot (gem-quality olivine). Some were 12 millimeters in length. I also found peridot in place that were nearly 0.5 inch across.
Even though olivine had been recognized in this area >100 years ago, no one had ever looked at the quality of the olivine. Later, I mapped the Leucite Hills and identified all of the olivine bearing volcanoes.