EPIDOTE: GREEN MONSTER MINE, ALASKA

Today a song popped up on the radio that remined me of a famous mineral collecting duo.  The crooner was Buck Owens, the song was Together Again, and the collectors were Art Montgomery and  Edwin Over.  I have previously commented on some of their expeditions and here is another blurb.

The year was 1936 (had to be summer) and Ed and Art were heading to the Prince of Wales Island along the coast of southeast Alaska (Berry, 2002).  The objective of this trip was to collect epidote crystals near Green Monster Mountain (perhaps inspired by the 1935 Smithsonian expedition), a former lead-copper-silver mining area where epidote crystals had been collected since around 1915; Ed and Art were off on anther adventure.  I keep thinking that 1936 was 80 years ago when tents were probably made of heavy canvas, the camping equipment would have been primitive (compared to today’s standards---no REI rain slickers), and work was in a coastal rain forest where temps are cool, humidity high, and rain plentiful (~95 inches per year). Tom Loomis from Dakota Matrix noted that the Green Monster Mountain epidote is some of the best in the world, and there are numerous epidote localities. Epidote from this locality should be coveted not only because of their quality but because of the effort it probably took to obtain specimens. If the mosquitoes don't get you at this locality the grizzly bears and green monsters will - in the pouring rain. 

The rocks that produce the epidote are mineralized marbles of the Wales Group (dates around 541 Ma, just about the Cambrian-Precambrian boundary) that have been cooked (contact metamorphism, high temperature) by Cretaceous granodiorite intrusions.  These types of deposits are known as skarns and at Green Monster Mountain specifically as garnet-epidote-diopside skarn meaning these metamorphic minerals are present and are associated with migrating hydrothermal solutions.   On a larger scale, garnet-epidote-diopside skarns are part of a larger group known as Copper Skarns that form close to intrusions and at/near plate subduction/transition zones (Meinert and Dawson, date unknown). Prince of Wales Island is near the Queen Charlotte Fault that runs from the Cascades (U.S. mainland) to mainland Alaska.  It is a transform fault (like the San Andreas) where the Pacific Plate is sliding past the North American Plate and is tectonically active.

I don’t have the slightest idea where Over and Montgomery prospected as epidote mines/diggings seem to be scattered over a wide area.  For example, Herreid and others (1978) stated: “the principal productive mineral deposits in the area are skarns containing copper, zinc, molybdenum, and gold around the Copper Mountain pluton (Cretaceous). The largest known deposit, the Jumbo Mine, produced 10,194,264 lb of copper, 87,778 oz of silver, and 7,676 oz of gold during the first part of the century (Kennedy, 1963). Museum-quality epidote and quartz crystals have been won from the skarns around the pluton.”

Kennedy (1963) also noted the Jumbo Mine deposits are famous for their epidote crystals. “Locally epidote is an abundant mineral in the skarn zone at the Jumbo Mine. It occurs as medium-sized irregular grains replacing garnet, in groups of radiating crystals surrounded by later quartz and calcite, and as coarse crystals of exceptional beauty and complexity of crystal form lining the walls of vugs. The epidote specimens from the Jumbo area are rivaled only by those on the Tyrol [epidote discovered in 1865 in Austria and often considered the world’s best]."

The epidote locality noted by MinDat at Green Monster Mountain is the Rex Prospect (Idela Prospect): “this prospect consists of three short caved adits and some pits and trenches that probably date from before WW I. All or most are on a large block of (14?) patented claims that extends northwest to the Green Monster Mine (CR153). The deposit consists of mineralized zones along faults in garnet-epidote-diopside skarn.”  

Epidote and quartz from Green Monster Mine, Alaska.  Width of photo ~8.0 cm.

I purchased my epidote quartz specimen a couple of years ago at the CSMS summer show from Terra Minerals who had received a flat from Jack Crawford; I thought mine was the best of the bunch!  The specimen is a mass of slender green epidote crystals whose numerous and non-orientated positions are known as jackstraw crystals are “going in every which direction.”  There is also a larger  terminated quartz crystal that has included epidote crystals.  One of the more interesting aspects of the specimen is a single epidote crystal that is only partially inserted into the quartz crystal.  I presume, but am not certain, that the epidote crystals formed before the quartz and are what The Quartz Page (http://www.quartzpage.de/inc_text.html) refers to as protogenetic inclusions. One characteristic of these epidote-first inclusions is that included fibers run through the entire crystal at random orientations. 

Terminated quartz crystal with epidote inclusions.  Width of photomicrograph ~8 mm.

Jackstraw arrangement of epidote crystals.  Width
of photomicrograph ~8 mm.

Jackstraw arrangement of epidote crystals.  Width
of photomicrograph ~8 mm.

Note the different sizes of epidote crystal. The lower mass are "needles."  Width ~8 mm.

 In addition, there are numerous smaller and doubly terminated quartz crystals scattered around.  It is one of the more aesthetically pleasing specimens in my collection.

Note the large single crystal of epidote partially included in the quartz crystal.

 Epidote, a calcium-aluminum-iron silicate, is not an uncommon mineral occurring in a wide variety of metamorphic and igneous rocks; however, most specimens for sale at shows generally are large terminated (wedge variations) and lustrous green single crystals or “medium size” elongated and interconnected (jackstraw) crystals.  Some specimens containing numerous crystals are quire large measuring in several centimeters and make impressive displays.  Most of my previous epidote crystals were collected (with better knees) from the Calumet Iron Mine near Buena Vista in Chaffee, County, Colorado (see Post May 1, 2013).

Epidote almost always occurs in some shade of green and most collectors immediately recognize specimens that are the common pistachio green color. However, colors can range to almost a black to yellow to brown and all sorts of shades in-between.  Crystals leave a white/clear streak and are slightly softer than quartz at ~6.5 (Mohs).  They usually have a vitreous luster and darker colors are opaque while the very light shades are translucent/transparent. Epidote (Al/Fe-rich) is in solid solution (a transition) with clinozoisite (Al-rich) and it is often tough to distinguish between the two minerals.  Epidote is “usually” darker in color due to a higher iron content while clinozoisite is a “lighter” shade due to less iron in the mineral and more aluminum.  In addition, several members of the Epidote Supergroup are variations of the basic epidote.  Some have legitimate mineral names such as hancockite (enriched with lead) while others are simply noted as epidote-(Sr) and enriched with strontium.  All are similar “looking” (commonly prismatic crystals) and belong to the Monoclinic Crystal System.

AFTERTHOUGHTS

I simply find it amazing that the early collectors (including paleontologists) were able to access sites across the world with minimal support help.  I presume Over and Montgomery traveled to Prince of Wales Island by ship.  Did they then pack in collecting and camping equipment with animals or on their back? Did they employ "sherpas"?   How did they wrap and pack out specimens? Did they worry about grizzly bears? Today the Island only has about 5000 human inhabitants and Craig is the largest population center at 1500. Is Green Monster Mountain close enough to supply centers?  All of these, and more, are some of life’s persistent questions.

I don’t have access to papers or notes relating to the Alaskan Expedition. In fact, I was uncertain if Montgomery went to Alaska or if he stayed in New York to sell specimens.  However, George White (Berry, 2002) stated, “Other outstanding discoveries were made by the pair…Prince of Wales Alaskan epidote in 1936” and Crosby (2015) noted that “1936 brought new energy into the canyon [Clay Canyon in Utah collecting for variscite] with the entry of Arthur Montgomery and Edwin Over who had just been collecting epidote at Green Monster Mountain on Prince of Wales Island, Alaska.” 

REFERENCES CITED

Berry, R., 2002, History of the Colorado Springs Mineralogical Society: privately printed.

Crosby, D., 2015, Clay Canyon and the Little Green Monster variscite mine: www.mindat.org. 

Herreid, Gordon, Bundtzen, T.K., and Turner, D.L.,1978, Geology and geochemistry of the Craig A-2 quadrangle, Prince of Wales Island, southeastern Alaska. Alaska Division of Geological and Geophysical Surveys Geologic Report 48 p.

Kennedy, G.C., 1953, Geology and mineral deposits of the Jumbo Basin, southeastern Alaska: U.S. Geological Survey Professional Paper 251.

Meinert, L., Dawson, K., retrieved January 2019: http://earthsci.org/mineral/mindep/skarn/skarn.html         

PHENAKITE: LAZARD CAHN AND WILLARD WULFF

 

High altitude gem collecting on Mt. Antero.

In a recent Post (Dec. 19, 2018) I noted that Edwin Over was a Charter Member of the Colorado Springs Mineralogical Society, one of the country’s oldest rock and mineral societies dating back to inception in 1936.  Mr. Over was a mineral collector of some fame but evidently was not recognizable by many.  It seems as Ed preferred to spend his time in the field collecting as a “lone wolf” (Wilson, 2018) while avoiding the lights and glamor of the cities and auctions.  His best-known field collaboration was with Art Montgomery, a productive union that lasted from ~1934-1941 (see Dec. 19 Post).  One of their collecting localities was on Mt. Antero in Chaffee County, Colorado, in the Sawatch Range near Buena Vista.  The Mt. Antero-Mt. White localities, first discovered in the mid-1880s, are perhaps the highest (elevation) gem collecting sites in the U.S. at nearly 14,000 feet and are “most famous” for aquamarine (blue beryl, Be₃Al₂Si₆O₈, with a chromophore of Fe++ or ferrous iron).  Pearl (1972) noted that Over maintained a camp “near/on” Mt. Antero and collected in summers 1928, 1931, 1932, 1933, 1938, 1951, and 1953; the 1938 expedition was spent with Montgomery. Other than the beryl, the Mt Antero sites have produced beautiful specimens of smoky and clear quartz, various feldspars, muscovite, monazite, fluorite, bertrandite, phenakite and others.  Check out the newsletter of the Colorado Mineral Society for additional information: http://www.coloradomineralsociety.org/newsletters/March2014.pdf  

 

Prospecting for aquamarine on Mt. Antero.

When I first moved to Colorado and started changing my collecting interests from fossils to minerals, I became intrigued with Mt. Antero and decided that would be my first 14er and perhaps even an aquamarine would show up.  I was also sort of fascinated by the mineral phenakite, as in what kind of mineral is that creature, and is it spelled with a “k” or “c” (k is correct). It turns out that CSMS was sponsoring a collecting field trip to the aquamarine sites and so off I went a few days early to secure a camp site, check out the area, and make the trek to the summit ON FOOT.  No cheating for me since I wanted the experience of hiking; however, on the day of collecting I was able to drive an ATV to the main sites at ~13,500 feet and wander all over Antero, Mt. White, Carbonate Peak, and a few other high points. I was able to pick up a few small broken crystals of aquamarine, some terminated smoky and crystal quartz crystals, and a few non-colored beryl crystals. 

On a subsequent trip I located a couple of terminated quartz crystals with a few much smaller, gemmy, crystals attached to the quartz.  Without magnification I simply wrote off these smaller crystals as quartz (phenakite comes from the Greek phenakos meaning deceiver since it “looks like quartz” :), or maybe even clear topaz.  Upon returning home and taking a closer look under a binoc scope, and browsing photos in MinDat, I guessed/identified phenakite as the mystery mineral.  Now, as an old softrocker and paleo person from the plains, I didn’t have the slightest idea what phenakite was or is.  This was early in my career as a mineral collector and we certainly did not have phenakite in Kansas!  Probably not even in the Mineralogy class collection drawers!

Phenakite crystal attached to quartz.  Width of crystal ~3 mm.

Phenakite crystal attached to quartz.  Length of crystal ~3 mm.

Phenakite crystal (cube like) attached to quartz.  Width of crystal ~2 mm.

Phenakite is a beryllium silicate [Be₂SiO₄] that is present in the beryllium-rich granite pegmatite emplaced on Mt. Antero.  Other beryllium minerals at Mt. Antero include topaz and bertrandite (beryllium silicate hydroxide).   Chrysoberyl (see Post July 22, 2016), herderite (see Post August 24, 2018) and pezzottaite (see Post April 29, 2018) are other lithium minerals that have caught my eye.

It is difficult to describe phenakite other than saying keep a sharp eye if prospecting in a lithium rich pegmatite or high temperature metamorphic rocks.  Most crystals are small but some range up to several inches in length (rare). One very confusing identification facet is their habit (Trigonal Crystal System), ranging from prismatic (long) to tabular to modified and/or flattened rhombohedrons.  Crystals are often clear and gemmy; however, they may take on a white to pale yellow color.  The gemmy crystals ate transparent while white crystals are more translucent. They have a vitreous or shiny luster and are quite hard at nearly 8.0 (Mohs). Specimens are quite brittle and break with a conchoidal fracture.  The crystals from Mount Antero are generally small and attached to quartz crystals and seem to be modified rhombohedrons.  However, individual and unattached crystals are found by the dedicated aquamarine hunters and if large enough are faceted and bring a healthy price as gemstones. At other localities phenakite is massive or granular---and really tough to identify.

Unattached phenakite crystal.  Width ~ 8mm.

As noted several times, I am far from a mineralogist and have my difficulties with crystallography, some identifications and descriptions.  If you really want to learn about phenakite check out my colleague Bob Carnein’s article in the September 2015 issue of the Lake George Gem and Mineral Club.  It will make you weep with joy—if you are interested in phenakite!

Prismatic terminated phenakite crystal, length ~4 mm, embedded on crystals of colorless fluorite.  Mass attached to quartz not shown on photo. The Cahn-Wulff specimen.

The real reason that I decided to write this little blurb is the historical significance of one specimen I purchased at an estate sale.  Traveling back to 1936 and the formation of CSMS I find that three of the Charter Members were Lazard Cahn (see Post Sept. 17, 2015)), Edwin Over (see Post December 19, 2018) and Willard Wulff (see Post July 28, 2016).  The phenakite crystal I have is a micromount owned by Lazard  Cahn (d. 1940) and then traded/sold to Willard Wulff.  I can only dream that Cahn acquired the specimen from Ed Over, then passed it on to Wulff, then to his daughter, and it now resides in my small collection.  Now that would be a story!

Go out and chase your dreams no matter how crazy it looks.

                               Shanice Williams

REFERENCES CITED 

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Pearl, R. M., 1972, Colorado Gem Trails and Mineral Guide: Swallow Press, Ohio University Press, Athens.

Wilson, Wendell E., 2018, Mineralogical Record Biographical archive: www.mineralogicalrecord.com.