HAPPY NATIONAL FOSSIL DAY

 

CELEBRATE OUR PALEONTOLOGICAL

HERITAGE

HAPPY NATIONAL FOSSIL DAY

Looking for the little creatures

Field crew, San Rafael Swell,

Central Utah; late 1980s

WHAT'S IN THE SUBSURFACE: ELK CREEK CARBONATITE & REE

Summer 2025 has slipped away without so much of a goodbye or a  Fall hello. The Fall Equinox was a few days ago on September 22^nd and was marked, in my life, by a tough session of physical therapy. October is here, the full moon on October 7 is known as the Hunter’s Moon, and one of my favorite days is scheduled for the end of the month, Halloween. In my younger days October was a time for field trips with camping, smoky fires with sizzling burgers, old collecting stories, a mild overnight frost, and the fabulous smell of coffee in the cool morning.

October, for me, is also a time for evening reads of older authors, especially writers like Washington Irving describing the Catskill Mountains and its people--  Rip Van Winkle was one of those happy mortals, of foolish, well-oiled dispositions, who take the world easy, a simple, good-natured man and a kind neighbor. Next up on the list is one that frightened my children at a young age---"The Legend of Sleepy Hollow." Even today I prefer not to walk in the woods at night while remembering the words: All these, however, were mere terrors of the night, phantoms of the mind that walk in darkness. 

On a more serious note this has been an interesting summer, to say the least. Personally, it was the summer where I lost my original left knee, and had it replaced by some sort of metal (?titanium) substitute (hence celebrating the equinox with somewhat painful PT). That project makes my joints more symmetrical since the new replacement joins both hips and the right knee sporting new hardware! They look good lighting up the scanners. On the weird national front there are numerous possibilities that “could take the cake”; however, my choice for spooky happenings in the country---our federal administration deciding that the U.S. should “take over” Greenland, by “hook or crook”. Evidently someone in D.C. woke up, several years too late, and discovered China has a foothold on many Rare Earth Elements (REE) and Critical Minerals (see July 24th Post on antimony). Wow, what do we do now? I got it, we will just nab Greenland and its mineral wealth. Forget about its relationship with NATO friend Denmark. So, it goes on and on!

But back to reality, and perhaps a much better solution than making enemies, has been to watch the progress associated with the Elk Creek REE-Critical Minerals project in far southeastern Nebraska. 

 

The newspapers and Wall Street financiers (at least some of them) have noted the project is the largest niobium and the second largest proven Rare Earth Elements (REE) mine project in the U.S. Someone in Washington, a Rip Van Winkle sort of chap, awoke after 20 years and interpreted his dream that REE were needed for a gazillion high tech products in both civilian and defense applications. The movers and shakers, having been immersed in cultural wars rather than development, suddenly realized that the U.S. must import our supply of REE/Critical Minerals from several different countries although most comes from China. Now, if a REE producing country decides to close the mineral spigot coming to the U.S, well that is serious business.  Again, see the July 24th post on antimony.

So, the discovery of this REE/Critical Minerals deposit in rural Nebraska is a very major event for our country. The company operating/owning the deposit is Colorado-based NioCorp, a play on one of the major elements of interest, niobium.  According to NioCorp the Elk Creek project is “shovel ready” although they continue to hunt for additional funding needed for a complete move to commercial operations.

The chart below is from a NioCorp prospectus and lists the major minerals, along with their projected tonnage, during a projected mine life span of 30+ years.

 

Morningstar.com, in accessing the stock value of NioCorp, has a more detailed explanation of the minerals. “Niobium is used to produce specialty alloys as well as High Strength, Low Alloy steel, which is a lighter, stronger steel used in automotive, structural, and pipeline applications. Scandium is a specialty metal that can be combined with aluminum to make alloys with increased strength and improved corrosion resistance. Scandium is also a critical component of advanced solid oxide fuel cells. Titanium is used in various lightweight alloys and is a key component of pigments used in paper, paint and plastics and is also used for aerospace applications, armor, and medical implants. Magnetic rare earths, such as neodymium, praseodymium, terbium, and dysprosium are critical to the making of neodymium-iron-boron magnets, which are used across a wide variety of defense and civilian applications.”

Since this is a science blog, what about the geological setting? OK. The REE/Critical Minerals project is located within a rock unit termed the Elk Creek Carbonatite, a type of interesting, intrusive, igneous rock composed of at least 50% carbonate minerals. At Elk Creek these carbonate minerals are primarily dolomite, calcite, and ankerite with accessory barite, ilmenite, rutile, quartz and others. Blessington and others (2022) described the carbonatite as "a multilithologic carbonatite comprised of an early apatite-dolomite carbonatite, a middle/heavy REE-enriched magnetite-dolomite carbonatite, and a late-stage light REE-enriched, barite-dolomite carbonatite," The carbonatite was intruded into the older Precambrian (Proterozoic) igneous and metamorphic rocks that form the “basement rocks” of southern Nebraska. These country rocks at Elk Creek represent the suturing of Proterozoic island arcs onto the older more stable craton (Laurentia) to the north.

Carlson and Treves (2005) described the carbonatite as lower Paleozoic in age (Cambrian). In addition, Peterman (Z. E. Peterman, personal communication to Carlson, 1985) dated a biotite from the carbonatite as ~544 Ma (Cambrian).  The intrusion and the basement rocks are now covered with about 200 m of Pennsylvanian marine sedimentary rocks and lesser amounts of glacial drift. That fact indicates that post-Cambrian sedimentary rocks are absent from the intrusion and the basement rocks until the Pennsylvanian marine rocks appear. There is no surficial representation of the carbonatite intrusion.

However, the question now becomes, were pre-Pennsylvanian rocks once present in the Elk Creek area? That is a type of question that I encouraged my students to ask. Don't let the instructor just stop with that positive statement about the presence of later Paleozoic rocks. In my olden days of grad school (pre-plate tectonics days) we  often referred to a Paleozoic, high platform area (a positive area) trending southwest to northeast through the center of the country as the Transcontinental Arch. Here Paleozoic rocks were thin or absent due to periodic rejuvenation of basement highs. Students assumed that a  section of Paleozoic sediments were deposited in the central part of the U.S. but were thinned or destroyed by erosion during uplift. One of my favorite grad school classes was taught by the the famous (at least to geologists in the 1940s through 1970s) geologist Armand J. Eardley using his book Structural Geology of North America. Later seismic work associated with exploratory drilling indicates that smaller scale transverse (to the Transcontinental Arch), basement controlled, tectonic features probably had significant control on depositional patterns (Carlson, 1999). In addition, later Paleozoic uplift of the Nemaha Ridge was most likely responsible for the destruction of earlier Paleozoic rocks from the Elk Creek area (see later discussion on Nemaha Ridge). 

 A little prior history.

Back in the late 1960s (my undergrad days) and early 1970s (my early teaching days) surficial igneous rocks were virtually unknown in Kansas with the exception of a few exposures of kimberlite diatremes in northeastern part of the state near Manhatten, and the strange occurrence of lamproite (ultrapotassic, mantle-derived, volcanic or subvolcanic rocks) intrusions in southeastern Kansas—the Rose and Silver City Domes. The diatremes are pipe-like (shape) structures containing igneous rocks that originated deep in the earth, maybe 100-400 miles, and exploded to the surface in a very short time. They are of great interest to geologists for a number of reasons, not the least of which is that most diamonds in the world are found in these structures—i.e. those in South Africa. So, I always took my students on field trips to Riley County, near Manhattan, to examine these features and allow them to collect small garnets from the known (at that time) exposures. 

The Kansas diatremes are part of the Central North American Kimberlites Field stretching about 3000 miles from Somerset Island in the Canadian Arctic Archipelago (Nunavut) south through the Saskatchewan fields and ending in Riley And Marshall Counties in northeast Kansas. The kimberlites in this corridor are mid-Cretaceous in age (~105-95 Ma). All structures are located at the highly attenuated lithospheric edge of the North American Craton, facilitating edge-driven convection (Kjarsgaard and others, 2017). 

NOTE: I can assure you that in 1971, or in 2025, I was not familiar with Edge Driven Convection :) 

At about the same time as we were collecting garnets, the Nebraska Conservation and Survey Division, along with the USGS, were flying aeromagnetic surveys (pulling a magnetometer behind the plane) over the southeastern part of the state trying to see if the emplacements of the Kansas diatremes, now known to number 13 in 2025, continued into Nebraska. The igneous kimberlites contain ultrabasic rocks that produce a positive magnetic high. Their quest was unsuccessful; however, they did discover a “vertical gravity gradient high” (Drenth, 2014) over Elk Creek where later drilling confirmed the presence of the carbonatite intrusion.

Early on MolyCorp and Cominco American both investigated the economic potential of the carbonatite. In 2010 Quantum (now NioCorp, name changed in 2013) acquired the mineral rights and started drilling, that continues today, with plans to construct an underground mine and harvest REE and Critical Minerals. 

The mineralization of the REE (https://miningdataonline.com/ ) is within the Rare Earth Minerals:

 • Bastnäsite ([Ce,La,Y]CO3F);
• Parisite (Ca[Ce,La]2[CO3]3F2);
• Synchysite (Ca(Ce,La)(CO3)2 F);
• Monazite ([Ce,La]PO4).

The niobium, titanium, and scandium mineralization zones are found scattered throughout the carbonatite although most niobium comes from niobium-rich Pyrochlore Supergroup minerals, disseminated and included, in ilmenite and magnetite. (open access papers at PorterGeo.com).

Carlson and Treves (2005), in describing the tectonics of the area in relationship to the carbonatite intrusion, noted the following framework (see diagram below). The country rocks are composed of low to medium grade metamorphic gneiss and schist of island arc origin with ages ~1.84 to1.71 Ga. Igneous granitic intrusions came along about 1.78 to 1.35 Ma. The intrusion of the ~544 Ma carbonatite likely was influenced by several (probably all related) nearby features (see figure below): 1) the Mid Continent Rift System (MRZ ~1.2 Ga), a failed continental rift extending from Oklahoma northeast to Lake Superior and beyond (see Posting October 31, 2013); 2) the buried boundary sutures of two Precambrian terrains (mountain building events) termed the Penokean Orogen (1.84) (with exposures in Wisconsin and Minnesota and subsurface accretions to the south)), and the Central Plains Orogen (1.78 Ma), Proterozoic mountains now preserved in the subsurface of Kansas, Nebraska, and Missouri; 3) the Nemaha Ridge or Anticline, a buried granite high associated with a larger tectonic/structural zone trending almost north-south from Oklahoma City to Omaha. The Ridge is faulted along the sides and runs parallel to the MCZ located about 40 miles to the west. Its association with the MRZ might indicate isostatic uplift was responsible for the elevation of this strange ridge. Parallel to the Ridge is the large Humbolt Fault System, the source for most of the small Kansas earthquakes,  The Elk Creek Carbonatite was intruded very close to the crest of the Anticline which was then responsible for destroying the early and middle Paleozoic rocks.  The age of the Nemaha uplift seems centered at around 300 Ma.

 

This map shows the intersections of Penokean Orogen rocks in the northeast, Central Plains Orogen rocks in the southwest, dark gray Nemaha Ridge, and light gray Mid Continent Rift Zone. All of these tectonic zones are related (my understanding) to/with a multitude of basement tectonics.

 

Simplified cross section of Nemaha Uplift after Steeples, 1982. According to Carlson and Treves (2005) early and middle Paleozoic rocks are absent at the Elk Creek Carbonatite since the intrusion is very near the center of the uplift. As Don Steeples, my old friend from long ago college days, would say,"who would expect a granite mountain range not far from the surface in Kansas? 

The Elk Creek Carbonatite also seems related to other carbonatites emplaced across North America ~550 Ma. All seem related to deep seated suture zones similar to those in the Elk Creek accretionary material along the southern extension of the Penokean Orogen near its boundary with the Central States Orogen. Evidently a rejuvenation of these suture zones during the Cambrian allowed for the emplacement of the carbonatites (Carlson and Treves, 2005).

So, with all the news about a lack of REE/Critical Minerals being mined in the U.S., and our dangerous reliance with somewhat unfriendly foreign entities, it would seem that the Elk Creek project has a better than average change of succeeding. I guess only time will tell.

Meanwhile, as I think about dumb stuff, the situation is getting worse (Hirukuma). If I think about good stuff my mind goes on a whirlwind and that is why I tried to tackle this difficult (for me) writing adventure. I am "way outta" my comfort zone with Ridge Driven Convection and carbonatites. But, this has been a tremendous learning experience for an old plugger like me. At times my mind does a few cartwheels trying to assimilate some of the info. However, cartwheels keep the ole mind in gear and rumbling down the road and not stagnating. I hope readers can understand what I am trying to explain, and understanding that the discovery of Elk creek is exciting. Not only exciting for what Elk Creek may produce, but exciting to think about the decades long perseverance of generations of geologists who brought the project to fruition (we hope). 

I also hope that readers will examine some of the references listed below. I could not have written a complete paragraph without consulting numerous professional papers written by geologists "much smarter than me." So, I offer them my sincere thanks for their fantastic presentations.  

REFERENCES CITED

Blessington, M., Johnson, C., Koenig, A., Farmer, G., Kettler, R., Verplanck, P., & Lowers, H., 2022, Petrogenesis and rare earth element mineralization of the Elk Creek carbonatite, Nebraska, USA: Ore Geology Reviews, vol. 146. 

 Carlson, M.P., 1999, Transcontinental Arch--a pattern formed by rejuvenation of local features across central North America: Tectonophysics, vol. 305,  issues. 1-3.

Carlson, M.P. and S.B. Treves, 2005, The Elk Creek Carbonatite, southeast Nebraska--an overview: Natural Resources Research, vol. 14, no.1. 

Drenth, B.J., 2014, Geophysical expression of a buried niobium and rare earth element deposit: The Elk Creek carbonatite, Nebraska, USA: Interpretation, vol. 2, issue 4.

Kjarsgaard, B.A., L.M. Heaman, C Sarkar, and D.G. Pearson, 2017, The North America mid-Cretaceous kimberlite corridor: Wet, edge-driven decompression melting of an OIB-type deep mantle source: Geochemistry, Geophysics, Geosystems, vol. 18, issue 7.

Steeples, D. W., 1989, Geophysics in Kansas: Kansas Geological Survey, Bulletin 226.

NEWS FROM THE STRANGE, SCARY, STUPID AND UNKNOWN: TARIFFS

 On the 14^th of August a note in the Community Discussions section of mindat.org appeared and it is rather scary, at least if you sell or purchase minerals. As usual, a decree issued in Washington can cause mass confusion and angst out here in the hinterland. What makes the decree scary: Every incoming mineral shipment—even low-value mineral parcels—now faces U.S. import duties and tariffs. The De Minimis exemption ($800 threshold) was suspended for all countries on August 29, 2025. And, it seems that both mineral dealers and buyers are confused about the modus operandi of the tariffs. The following material was abstracted from the MinDat discussions (ongoing) with the original statements submitted by Mark Wrigley who is associated with the mineral auction site at e-rocks/com

 Mark notes there is a lot of confusion out there about the new U.S. tariffs now in place and how this affects us mineral people and our community of interest. Over at e-Rocks we will see some of the likely fallout from this over the next weeks and months so have built a website for anyone to use to understand the different tariffs and new declarations and send/receiving options that are evolving. The site is tariff.rocks and is available to all.

For most readers of this Blog, the export of minerals is of a minor consequence. As it stands, no one really knows what is going to happen except that U.S. exports will no doubt be handled differently in different countries - currently the EU is quite hot at collecting VAT at the border but not 100%, The U.K., a little more relaxed, other places like Australia no problem as there are generous value allowances. This is likely to change in reciprocity to the U.S. Tariffs.

But most of us will be interested with the imports-buying a mineral  specimen requiring shipping to the U.S. Fo one thing the $800 value (no tariffs on items under $800) allowance will go and the tariff will be added depending on where the package is coming from. Evidently, if the tariff is not paid by seller, the  packages will either get through unchecked with a payment on delivery fee of $80-$200 per package depending on country of origin, or checked = Tariff % added plus $8.85 fee charged to the receiver on delivery. So, if the tariff is not paid by the seller then the U.S buyer will pay. How much? Well, a mineral sent by our friends in Canada will cost our U.S collectors a tariff of 35% plus delivery fees, I presume. These fees are likely to cause a large number of “return to sender” parcels as the buyer receives such (large amounts of money) in the mail..

 Perhaps readers thought that tariffs imposed by the U.S. would only cause the price on a well-constructed Japanese or German car world increase in buying price. Well, guess again. Yes, we will pay a premium price on our next new vehicle but also on that new teeny-weeny micromount, and no, the foreign sellers will not fork over the increase as promised (sort of like who will pay for the border wall? Mexico). You, the small-time mineral collector who just wants to buy a nice pyrite specimen, is going to pay. And depending on current country of seller, tariffs rates could be substantial.

 For now, the mineral trading community, and the many small-scale rockhounds, face a new reality: higher costs, fewer shipping options, and zero tolerance for documentation errors. And, don’t even think ask about a gift exemption unless you want someone knocking down your front door wanting to view documentation. And, how will this affect the Tucson shows, and the large number of club shows? If the vendor at a local show buys specimens with an international origin (that is, they purchased from abroad) their costs and selling prices must increase. Will buys pay the extra amount or just turn away? I guess only time will tell.

 My suggestion to readers is to log in to MinDat, move over to Community Discussion, and check the August 14 date. Also, Mark may be able to answer more specific discussions over at e-rocks. Com.

 WAIT A MOMENT, HOT OFF THE PRESS: A federal U.S. appeals court just ruled all of Trump's tariffs illegal... so here comes an appeal and a longer wait to find out what's next. 

 

And that my fellow rockhounds is about the limit of my knowledge about tariffs on minerals. Whoda thought?

WOLF CREEK PASS: COLLECTING MORDENITE AND HAULIN' CHICKENS

 

Me and Earl was haulin' chickens
On the flatbed out of Wiggins 
And we'd spent all night on the uphill side                                                                                                               
Of 37 miles of hell called Wolf Creek Pass
Which is up on the Great Divide

At one time, way back in the 1960s and 1970s, it seemed like the “whole world, or at least most of the U.S., had heard of Wolf Creek Pass near Pagosa Springs, Colorado, “up on the Great Divide.” The song was recorded/performed by Bill Fries under his nome de guer  of C.W. McCall and was a parody of “truck driven music” and CB radio chatter. The song reached #40 on the  U.S. Pop Top 40 in 1975 and followed on the heels of McCall’s  first successful commercial hit song: Old home filler-up an' keep on a-truckin' café. In case you are wondering, Fries had a previous successful gig in the upper Plains and Midwest hawking Old Home Bread.

Now we spied a sign, says eat gas now
We decided to whip in and pick up some chow
At the old home filler-up an' keep on a-truckin' café

But McCalls best known for his mega hit song Convoy described as a “first-person trucker spoken monologue, backed by a country arrangement.” Whatever, the song reached #1 in both the Country Western and Pop Charts for several weeks and made C.W. McCall a household name and started the CB Radio craze that swept through and over North America. Every kid, and many adults (mostly male), had a “handle” (CB Name) and practiced talking like nitwits: “Breaker breaker, one nine (meaning let me talk on CB channel 19).  Folks, we got us a fox in the henhouse” indicating someone had seen an unmarked law enforcement vehicle. The roadways were full of cars and vehicles with very tall radio antennas sprouting out of the back bumper.  It may seem rather simple but, you know, people were having fun and not worrying about tariffs, the destruction of National Parks, federal troops in the streets, or the Ukraine.

Breaker one-nine

This here’s the Rubber Duck

You got a copy on me Pig Pen, c’mon?

Mercy sakes alive, looks like we got us a convoy!

But, back to Wolf Creek Pass situated on one of the most scenic highways in the West, U.S 160 running from Walsenburg on the east side of the Colorado Front Range to Durango in the far southwest of the State. The scenery, geology, and historical sights along the 222 miles will fill your memory scrapbook. However, perhaps the best-known section of the road is from South Fork on the east over Wolf Creel Pass to Pagosa Springs on the west.

Wolf Creek Pass is located in the San Juan Mountains of southwestern Colorado, an area famous for voluminous mid-Tertiary volcanism. Geologists working for the USGS have written a number of scientific reports on the area based upon detailed mapping and skillful laboratory analyses of the rocks. They have mapped at least 22 major ignimbrite sheets and associated caldera structures active between 34 and 23 Ma. The scientists at USGS have described the volcanism as characterized by explosive ash flow eruptions resulting in collapse and the formation of calderas. Many of these calderas are associated with large scale ore deposits such as the Creede Caldera Complex. Probably the largest caldera, and perhaps the best known (at least to geologists) feature, is the massive La Garita Caldera formed when a “really large” supervolcano blew its stack and spewed out a guesstimate of 1,200 cubic miles of the Fish Creek Tuff  over at least 11,000 sq. miles around 28 Ma. The caldera itself is a oblong structure ~25 x ~50 miles in size.

I remain uncertain about the exact age of the volcanics at Wolf Creek Pass and their relationship to an extrusive caldera. The rocks are reasonably close to the Platoro Caldera near Summitville where the ejecta is generally referred to as the Treasure Mountain tuff; however, I cannot find evidence that the tuff extended to the Wolf Creek area. Perhaps the tuff is related to the La Garita eruption? Unfortunately, since moving to rural Wisconsin I do not have the resources of geology maps commonly found in Colorado research libraries.

Arnold Hampson wrote the definitive rockhound paper on Wolf Creek Pass collectable minerals and stated the host rock in the region is the Conejos Quartz Latite. However, over the past twenty years terminology has changed, and the Conejos is now listed as the Conejos Formation and is related to eruptions of the Platoro Caldera around 30 Ma. So, I am still confused about specifics and will place a call to the Acme Building looking for Guy Noir, Private Eye, to help answer one of life’s persistent questions (thanks to Garrison Keilor).

Treasure Falls, 105 feet of sheer beauty. Public Domain photo courtesy of Ahodges7.

The small number of samples in my collection came from near Treasure Falls, a 105-foot gorgeous stream of water tumbling through and over the volcanics and situated along U.S. 160 about 15 miles east of Pagosa Springs—over the crest of Wolf Creek Pass heading west. The Falls are a popular visiting site for travelers and therefore parking is at a premium for RVs and almost every time I motored over the Pass I was unable to park my bumper pull RV and missed out on collecting. However, there was one instance when I was able to pull over and scurry to pound on the rocks a couple of times. The best collecting site is about ¾ of a mile north of the Falls in exposures along the roadway.

MinDat lists 11 valid minerals and 12 other varietal mineral names that have been extracted from the four small collecting localities referred to as Wolf Creek Pass. Most of the attractive collected minerals are zeolites, and mordenite [(Na₂,Ca,K₂)₄(Al₈Si₄₀)O₉₆ · 28H₂O] is the most abundant and spectacular of the group. The mineral occurs as thin, white tufts and sprays of delicate acicular crystals that are silky to vitreous, and transparent to translucent. They are usually associated with amygdaloidal cavities in basalt where it commonly is “associated with black nontronite, green celadonite, and orange heulandite” (Hampson, 2004). Interestingly, Hanner (1976) described the Treasure Falls mordenite crystals as “some of the finest in North America.”

Width FOV ~12 mm.

Width of spray ~1.5 mm.

Width FOV ~5 mm.

Above photomicrographs of acicular mordenite sprays on dark green/black nontronite. The patch of green “spherules” to the right on lower is perhaps celadonite or, perhaps an unknown/listed copper mineral?  The orangish base of some sprays may be due to heulandite-Na.

Nontronite [Na_0.3Fe₂((Si,Al)₄O₁₀)(OH)₂ · nH₂O] is also a common mineral in the Wolf Creek basalts but is not a zeolite. It is the ferric iron-rich end member of the Smectite Group of clay minerals. It commonly mixes with celadonite to form dark green to dark brown aggregates in the basalt vugs. At other times it occurs as almost black (?darkest green) spheric aggregates. It is quite soft at ~2.0 Mohs and the aggregates are waxy to resinous and appear opaque. Their color and size make my photography difficult. Inherently, most specimens of nontronite at other localities are much lighter in color---yellow green, yellow orange, brown, and green.

Vug filled with black nontronite with a narrow “rind” of celadonite and a few acicular crystals of mordenite. Maximum length of vug ~2 mm.

The upper photomicrograph is a small (length ~15 mm), vug-filling, “concretion-like” specimen that “popped out” of the vesicle and was damaged on both ends. The inside the “concretion” is filled with spherical aggregates of darkest green nontronite. A second unknown appears as a silver colored, metallic luster mineral (see lower photo). The reflection from the light source is intense. My only guess is pyrite.

Another somewhat uncommon mineral, at least in Colorado, is the Mica Group mineral celadonite [K(MgFe³⁺◻)(Si₄O₁₀)(OH)₂}. In the Wolf Creek basalts it often mixes with nontronite as described above. At other times it is composed of waxy, dull, blue-green to olive green spherules lining the vugs. Black nontronite spheres and acicular mordenite crystals are often associated with the lined cavities.

Vug filled with darker nontronite and celadonite with a greenish-gray patch of celadonite on top. Width vug .75 mm.

 

Vugs filled with celadonite. Large vug ~ 1 mm.

The tiny saponite crystals appear as dust-like flakes in mordenite-filled vug (width ~5 mm).

A surprise mineral, at least to me, is saponite Ca_0.25(Mg,Fe)₃((Si,Al)₄O₁₀)(OH)₂·nH₂O], an aluminosilicate member of the Smectite Group of clay minerals. Although  it occurs in many colors and habits (from small subhedral crystals to massive to granular and points in-between), the specimens from Wolf Creek are quite tiny, greenish-brown, subhedral to “flakes” and difficult to photograph details with my equipment. But interestingly, at Wolf Creek the minute saponite crystals are suspended from the acicular mordenite crystals.

REFERENCES CITED

Hampson, A.G., 2004, Zeolites and associated minerals of the Wolf Creek Pass area: Rocks & Minerals, vol. 79. No. 5.

Hanner, M. E., 1976, Mordenite at Wolf Creek Pass: Mineralogical Record, vol. 7, no. 6.

Went down and around and around and down
We run outta ground at the edge of town
Bashed into the side of a feed store
In downtown Pagosa Springs