The Thomas Range Red Beryl Deposit
As we discovered last week, Red Emeralds formed 23 to 18 million years ago when "large-scale regional crustal extension and thinning…[caused] rhyolitic magmas [to] rise to the upper levels of the crust, where they are emplaced as shallow, subsurface domes…[Travel occurred through] a deep crustal fault zone along which mineralized magmas and fluids…were able to migrate toward the upper levels of the crust" (Shigley & Foord - 1984).
Essentially, red beryl deposits are giant "bubbles" of lava which came to rest beneath the surface of the Earth. Red Beryl has only ever been documented from three localities: The Black Range in New Mexico, the Thomas Range in Utah and the Wah-Wah Mountains in Utah.
Since the final resting place of these three rhyolite-lava "bubbles" is different, each magma "river" melted a channel through slightly dissimilar rock compositions on the journey to its final resting place, acquiring a mix of minerals along the way. The minor variance of this magmatic makeup causes crystals which exhibit unique characteristics in each locality. The Black Range produces small crystals sparsely, while heavily-included wafers are typical in the Thomas Range. Only the Wah-Wah deposit yields gem-quality material.
I visited the two Utah occurrences of Red Beryl in 2015, beginning with the Thomas Range deposit. Topaz Valley rests on public land less than five linear miles from the billion-dollar Brush-Wellman mining complex, one of the largest and only sources of concentrated beryllium in the world. Although beryl in rhyolite is uncommon to say the least, Red Beryl most likely formed in these Topaz-bearing rhyolites due to the high availability of atomically-unusual beryllium around this great crustal vein of almost incomprehensible size (Groat & Laurs - 2009).
Ruby Violet Claims vs Brush-Wellman footprint (Maps by Google).
$50-100M was spent on the red beryl mine; Brush-Wellman is a $1B+ site.
"These characteristics distinguish [topaz-rhyolites] from volcanic rocks of the middle and oldest groups in western Utah and imply a genetic relationship between the rhyolite and beryllium mineralization" (Lindsey - 1977).
The Rosette crystal habit is also called the Desert Rose, because this modified structure stacks crystal plates in a circular arrangement from a depressed center, like the petals of a Rose. Many species utilize this pattern to resolve low-water conditions, such as the Rosettes famously observed in the mineral Gypsum, which typically forms in arid regions.
Red Beryl has far less water in its crystal structure than typical beryl. Anhydrous crystal formation affects Thomas Range specimens more dramatically than examples from other localities. The hexagonal stacking on the termination end seen universally in this variety often displays strong Rosette patterning from this deposit.
Thomas Range Red Beryl Rosette with well-defined hexagonal levels,
originally collected by John Holfert and pierced by a Topaz Prism.
The only commercial Red Beryl mine has been closed more than fifteen years. Many new specimens entering the market originate from the public collection area on Topaz Mountain in the Thomas Range. "Rockhounds" are mineral collectors brave enough to confront the natural world and dig up specimens on their own.
Topaz Mountain is the Dana locality, which means the place of our original encounter; the same location Maynard Bixby made his discoveries. In the century since, Topaz Valley has produced many more stunning examples. Any discussion of this deposit would be remiss without mentioning the most prolific prospector in the range, avid rockhound John Holfert, whose Field Guide released in 1978 described in detail the diverse species which may be found here.
A Field Guide to Topaz and Associated Minerals of Topaz Mountain, Utah
by John Holfert
Upon arrival into Topaz Valley, one will enter a large amphitheater, facing a horseshoe of mountains surrounding everything in front. Looking to the ridge on the right, rockhounds have uncovered low-quality Aquamarine specimens. Looking to the ridge on the left, a white outcropping can be seen back in the middle. This area is known as the Cove, where some of the world's finest Red Beryl specimens are recovered by ordinary people.
No one needs to find the spot without assistance; the campers at the base of the trail do not receive many visitors, and they will happily show point out areas recent productivity to any new friend. Golden Topaz occurs everywhere in abundance, found on the ground just by walking around. To get your attention, light frequently flashes off sharp glassy faces bathing in the sun, gem bodies bleached white from exposure.
I was amazed from ground level how little has changed from historic online photos in the surface of Topaz Mountain. The ridge appears almost unscathed despite decades of nonstop, incessant scratching by humans. Many of the best and most significant specimens are still waiting here to be discovered.
Red Beryl deposit on Topaz Mountain. Note the rhyolite cavities at right.
Specimens are found in white stone with this pocked appearance.
Since "high-temperature (>600° C) lithophysal beryls are tabular as opposed to the significantly lower temperature, prismatic beryls, which are hydrothermal in origin" (Foord - 1996), the general consensus has been that Wah-Wah Red Beryl "growth occurred at temperatures below magmatic values (~300-650° C)" (Keith, Christiansen & Tingey - 1994). High-temperature environments most likely cool too quickly to allow large crystals to form, while low-temperature growth may be able to continue for a longer period of time.
The Thomas Range produces small tabular specimens almost exclusively, which would indicate formation occurred rapidly in a high-temperature environment. The presence of numerous grainy silicate inclusions creates a sandy appearance in many examples, and crystal surfaces are often covered by secondary quartz overgrowth. Thomas Range Specimens are translucent and orange in appearance.
The larger prismatic habits of the Wah-Wah locality suggests long-term formation at low-temperature, but most crystals are still tiny. Like pink diamonds, Red Emeralds are unusually small, with over 90% of faceted stones weighing between seven and eight points…seven to eight hundredths of a carat! (Kennecott - 1997) In sub-carat examples, both prisms and wafers are common. Wah-Wah Specimens are crystalline and purple in appearance.
At Left: Red-Orange Wafer Collage from the Thomas Range.
At Right: Red-Purple Wafer Collage from the Wah-Wah Deposit.
Although Utah beryl is red, this primary color has two secondary hues: Orange and Purple. Secondary means another color is mixed-in with the red. Thomas Range material regularly exhibits a hue which is a fire-engine red-orange. Wah-Wah tones appear predominantly reddish-purple. This is likely due to a slight variance in the availability of chemical materials used during formation.
Whatever the ingredients are in the volcanic soup required to produce red beryl, the combination of conditions in this recipe is so rare only one location has been found where the resulting crystals can be cut into precious gemstones: The Ruby Violet claims north of Bumblebee Mountain in the Wah-Wah Range of Beaver County, Utah.
When beryl grows under low-temperature conditions favorable to long-term crystallization, hexagonal wafers continue to stack one upon another until a tower has formed, which is called a prism. Although some prisms from the Thomas Range exist, almost all prismatic specimens are produced in the Wah-Wah Mountains. After the first 25 years of mining, the largest crystal ever discovered weighed only 30 carat and measured 22 millimeters in height by 12 millimeters in width and depth.
This 30.45 carat Lantern Twin with perpendicular sidecar measures
21.48 mm in height, 15.42 mm in width and 13.34 mm in depth.
Mineral rough must be facet-grade to shape a gemstone from its body. Specimens with too many inclusions cannot be fashioned into gemstones. While a lack of flaws may be the standard for Diamonds, all Emeralds have inclusions. Due to a lack of material, any Emeralds which can be rounded, polished or faceted usually are. Gem quality is judged on an evaluation of beauty which includes everything contained within a stone's body.
In Greece, gemstones were graded as if they were sections of water frozen in time. Whether this water originated near the surface of a pond or included more of the sediments one would expect near the bottom of a lake determined the overall quality of a stone. The Great Philosophers described gemstones of the highest crystalline purity as having the Finest Water.
In Zambia, the local word for Emerald rough of the highest quality is "Amish". When a television crew attempted to obtain this sort of facet-grade material, their guide defined the meaning of the word: "Amish is a local word meaning Water. Clear, clear like water."… Amish stones are the purest with no inclusions or marks. Only a tiny fraction of all Emeralds are Amish, and they are extremely valuable (Mine Hunters - 2016).
The mountain range where American Emeralds are found is the source of a natural spring originally located by Native American tribes. The indigenous name identifies both the spring and the mountain range today: "Wah-Wah " means "Good, Clear Water" (Van Cott - 1990).
Red Beryl gemstones from the second Utah locality are undeniably Emeralds, because they are literally born in the Finest Water!
Emerald's hexagonal shape reflects light without human assistance.
The highest quality crystals are engulfed in a richly-colored glow.
Next week the journey for red beryl specimens continues...come along and investigate the geologic history of this ultimate source: The Wah-Wah Mountains!
REFERENCES BY DATE OF INFORMATION
Tavernier, Jean Baptiste. Travels in India by Tavernier, Baron of Aubonne, Edited by William Crooke, pp. 44, 58 - 1925
Lindsey, David. Epithermal Beryllium Deposits in Water-Laid Tuff, Utah, Economic Geology - April 1977
Shigley, James & Foord, Eugene. Gem Quality Red Beryl from the Wah-Wah Mountains, Utah, Gems & Gemology - Winter 1984
Van Cott, J. W. Utah Place Names, University of Utah - 1990
Keith, Jeffrey, Christiansen, Eric & Tingey, David. Geological and Chemical Conditions of Formation of Red Beryl, Utah Geological Association, Publication 23, pp. 155-68 - 1994
Foord, Eugene. Geology, Mineralogy and Paragenesis of the Ruby Violet Red Beryl Deposit, Southern Wah-Wah Mountains, Beaver County, Utah, Kennecott Exploration Company - February 21, 1996
Monthly Production Summary of Actual Cut Stones. Weight Distribution Table by Size, Kennecott Exploration Company - January 13, 1997
Groat, Lee and Laurs, Brendan. Gem Formation, Production, and Exploration, Elements Magazine, pp. 153-8 - June 2009
Mine Hunters. Explosives and Emeralds, Discovery Channel, Season 1 Episode 8 - 2016
Mineral Entry: Gypsum. Mindat.org - Retrieved 2017