SODIUM-RICH ALKALINE MINERALS AND A RATTLED BRAIN

I am thinking that the pandemic fatigue finally rattled my fragile brain and caused some neurons to skip a beat.  The pandemic had kept me busy since March and I enjoyed sorting minerals, reading, writing articles, and contemplating future ideas.  And then boom, I received my second Covid vax toward the end of January and a terrific weight seemed lifted from my shoulders.  I really had no desire to do much of anything except look at minerals, read, and eat (all the unhealthy foods)!  And so, my Blog lagged, and postings were nonexistent for about six weeks.  Just not any enthusiasm for putting in the hours needed for a decent entry.  But then, slowly, my mojo started to return.  The days were getting longer (we recently passed the February Snow Full Moon), CSMS scheduled its rock and mineral show (usually in early June) for October 2021, the Rocky Mountain Federation, in conjunction with the American Federation, scheduled their annual meeting and show in Big Piney, Wyoming, for late June, a condensed “Tucson show” by ~80 dealers is scheduled for April, and I confirmed my fall camping reservation in the Black Hills. In addition, I joined the Baltimore Mineral Club and have actively participated in the Zoom meetings (and have made some new long-distance friends) and submitted an article for their newsletter.  But perhaps most interesting is that I discovered Mineral Talks LIVE appearing on Zoom each Wednesday at 1:00 PM EST (11:00 out here in the Mountains).  Each week a mineralogist/rockhound presents a “show and tell” about their collection (like Joe Dorris from the Springs or Alex Schauss from Tucson or Bruce Cairncross from South Africa), or a museum curator/curatrix, or a jewelry designer, or how to photograph minerals (Jeff Scovil).  The series has really perked me up.

Now, I still wear my mask, avoid crowds, stay out of most stores, and am constantly slathering on the hand sanitizer.  My family, friends and acquaintances stayed well and hopefully the worst is behind us (although I plead with persons to practice CDC suggestions), and to get their Vax.  So now, I need to start working on a post or two!

For years, even before I started collecting minerals (rather than fossils) I had “heard” of the famous Poudrette Quarry near Montreal, Quebec.  It was my limited understanding that the quarry produced “lots of” strange minerals; however, it was far away from my home and a quick field trip was out of the question. A few years ago, I purchased a nice mineral, carltonite, at the Tucson show for it beautiful blue color rather than for its collecting locality (Poudrette Quarry).  At about the same time I acquired several specimens needing to be “micromounted” and a few of these were from the Quarry—they were stuck in a drawer and remain unmounted.

After sort of coming out of my funk, I started scanning the internet and reading a variety of mineral and geology articles.  Somehow, I stumbled on a fantastic article about the Poudrette Quarry; that wobble in turn lead me to a mineral drawer where my specimens from Canada reside.  Yep, there were the Poudrette specimens stuck in the back of the drawer (and waiting to be mounted).  I had to take care of these!

GEOLOGICAL ASSOCIATION OF CANADA, MINERALOGICAL ASSOCIATION OF CANADA, 2006 JOINT ANNUAL MEETING MONTRÉAL, QUÉBEC

FIELD TRIP 4A: GUIDEBOOK, MINERALOGY AND GEOLOGY OF THE POUDRETTE QUARRY, MONT SAINT-HILAIRE, QUÉBEC

Charles Normand & Peter Tarassoff

Microsoft Word - GuidebookMSHfinal2-JP2.doc (mcgill.ca)

This field guide is an absolutely fantastic piece of work that nicely explains the intricacies of the geology and mineralogy of the Poudrette Quarry.  But beware, it is not for the faint of heart, those who might struggle with complex geological situations. I have read it several times trying to get a better understanding of Mont Saint-Hilaire—with only modest success.

I have abstracted the following information from this guidebook:     

The Poudrette quarry located in the East Hill suite of the Mont Saint-Hilaire alkaline complex (igneous rocks containing a high concentration of sodium and potassium, more so than in other igneous rocks and therefore containing feldspathoid minerals [lots of nepheline]) is one of the world’s most prolific mineral localities, with a species list exceeding 365 (MinDat now shows 433 valid minerals). No other locality in Canada, and very few in the world have produced as many species. With a current total of 50 type minerals (MinDat now lists 71 Type Minerals), the quarry has also produced more new species than any other locality in Canada, and accounts for about 25 per cent of all new species discovered in Canada.

Mont Saint-Hilaire is a small, roughly circular composite igneous intrusion rising some 375 meters above the surrounding Saint-Lawrence peneplain and measuring 3.6 kilometers in its widest part…The intrusion, physically a monadnock, is part of a series of Lower Cretaceous age intrusions collectively known as the Monteregian Hills.

The Monteregian Hills are related both temporally and chemically to partial melting of lherzolitic (ultramafic igneous rock containing much olivine often originating at about 200 miles deep in the earth’s mantle)  mantle by a rising thermal plume…during the late Cretaceous period. Based on 40Ar/39Ar data...the Monteregian Hills were emplaced during a single episode at about 124±1 Ma.

The mountain is separated into two major units. The western half of the mountain is composed of a concentric succession of a variety of gabbroic rocks which were emplaced first... The eastern half of the mountain, which represents the youngest part of the intrusion, comprises various types of peralkaline syenitic rocks (these rocks, syenites, are coarse grained, like granite, but contain very little quartz and have orthoclase as the dominant feldspar) and igneous breccias (the East Hill suite).

In common with other alkaline complexes, the primary reason for the large number of species found in the quarry is the agpaicity (the alkaline environment described below) of the rocks in the East Hill suite. The highly alkaline environment is characterized by the presence of sodium-rich feldspathoids, feldspars, pyroxenes, amphiboles and zeolites as primary minerals, and complex silicates containing titanium, zirconium, niobium, fluorine, and rare-earth elements (REE).

The specimens that I purchased are all minerals marked as being collected from the Poudrette Quarry.  Although there are a number of former and current quarry names, L.H. Horvath wrote (2019 in Mindat) “I would strongly advise that for now we keep the Poudrette quarry name, as it has been well established in the minds of collectors and in the mineralogical literature for the last 50 years. Furthermore, with few exceptions all the minerals (including recently described type minerals) on the species list below have been collected before 2007” (the year the Quarry was sold and renamed Carrière Mont Saint-Hilaire Quarry). My specimens are all sodium-rich silicates or carbonates with which I was unfamiliar---until I acquired new information after reading the field guide: normandite [NaCa(Mn,Fe)Ti,Nb,Zr)(Si₂O₇)OF], dawsonite [NaAlCO₃(OH)₂], and elpidite [Na₂ZrSi₆O₁₅-3H₂O].

The Poudrette Quarry is the Type Locality of normandite (1990), one of those sodium-rich, complex, rare-element silicates containing titanium, zirconium, and niobium along with fluorine that are found in alkaline igneous environments. Normandite occurs as tiny (often), yellow to orange, prismatic or fibrous crystals with a vitreous luster, It is tough to tell but crystals are transparent to translucent and have a measured hardness of 5-6 (Mohs).  My specimen containing normandite seems to be a dark gray nepheline syenite; however, that may be an erroneous guess.  The major mafic mineral in the syenite is some type of an amphibole with a nice bronze sheen under LED microscope lights.  My initial guess was aegirine, a pyroxene; however, the cleavage planes are closer to the 120 degrees typical of the amphiboles.

These photomicrographs of normandite, along with the black amphibole, are the best my camera could produce.  The yellow orange spot in the top is actually a cluster of tiny acicular crystals about .2 mm long (1/5 of a millimeter or about 1/64 of an inch).  In the second photo the longest crystal is about .3 mm long.
 

Elpidite is a hydrated sodium zirconium silicate occurring as a low temperature secondary hydrothermal mineral.  The prismatic crystals have a range of” pastel” colors; however, those on my specimen are sort of a dull white with a silky luster.  The crystals form in sprays or bundles although at times they are solitary. The mineral has a measured hardness of ~5 (Mohs) and diaphaneity ranges from opaque to translucent.  The crystals in my specimen are found as sprays/bundles in small cavities/vugs in a groundmass of ?albite/microcline.  Although the specimen is a small thumbnail, it contains a number of tiny minerals that my limited mineralogical skills will not allow me to identify!

Elpidite crystals in vugs: top, width of vug ~1.0 mm; middle, width of vug ~ 4.5 mm; bottom, width of vug ~2.0 mm.
 

Dawsonite is not a silicate like the previous two sodium-rich Poudrette minerals but is a low temperature, hydrothermal, sodium aluminum carbonate hydroxide.  At Mont Saint-Hilaire dawsonite is associated with the weathering of aluminum- and nepheline-rich rocks (feldspathic dikes and syenite). However, I first saw dawsonite as an authigenic mineral collected from the Eocene greater Green River lake sediments in Utah, Wyoming, and Colorado.  It was associated with alkaline oil shales and Smith and Milton (1966) noted that in some specimens dawsonite makes up ~25% by weight of the shale, contains ~35% of acid soluble Al₂O₃, and was viewed as a potential source of aluminum.  I completely forgot about dawsonite after completing that long-ago course in sedimentary petrology.

Cluster of prismatic dawsonite crystals.  Width FOV ~5.0 mm.
 

At the Poudrette Quarry dawsonite is mostly colorless to white, soft (~3 Mohs), transparent and leaves a white streak.  It has more of a silky luster that, at times, grades to vitreous, and forms encrustations or “clumps” of acicular or bladed crystals or tuffs of crystals.  Some dawsonite, at least in my specimen, effervesces in dilute HCl.

So, there it is, a measly three specimens from 433 known minerals from the Poudrette Quarry.  I can’t imagine what a collection of 400 or so must look like.  In fact, I really don’t know how many different minerals the largest Poudrette collection contains.  I am also unaware if collecting is still permitted.  I have read that no collecting is allowed, or that highly restricted collecting is sometimes permitted for a local rock club.

WORD OF THE DAY: agpaicity as in the agpaicity of the rocks in the East Hill suite.  Merriam-Webster: Definition of agpaite: any of a group of feldspathoid rocks (such as naujaites, lujauvrites, or kakortokites) from Ilimausak, Greenland, which differ from normal nephelite-syenites in having alumina in excess of the alkalies.  Merriam-Webster also noted that users of agpaite must love words since the only definition is in the unabridged dictionary.

At the next CSMS meeting, I will send a mineral specimen to any member that uses the noun or adjective in a grammatically correct sentence!  

 

REFERENCES CITED

Smith, J.W. and C. Milton, 1966, Dawsonite in the Green River Formation of Colorado: Economic Geology, v.61, no. 6.

 

PALYGORSKITE AND SEPIOLITE: BIRDS OF A FEATHER

 Get the facts first, then you can distort them as you please.              Mark Twain

Special Signed O. Ikibus Pegasus Emblem Meerschaum Pipe

Designed and sold by Royal Meerschaum

 I recently acquired a randomly selected collection of micromounts that I thought would be fun to explore.  However, I almost got myself in trouble with one of the mounts—palygorskite collected from the “Ohio Pit Mine, N. Ishpeming, Michigan in 1976 by acs.”  I thought, oh great, another Michigan specimen adding to my small collection from the UP.  I “sort of” knew that palygorskite was a clay mineral and assumed my specimen would “sort of” look like other clay minerals.  Now, I am far from experienced in working with clay minerals and about the only thing I remember from a sedimentary geology course was using deflocculates (?), maybe a water softener like Calgon (?), to break down mud rocks (composed of clay minerals). But that process is really stretching my brain cells.  In later life I simply gave the department mineralogist some of the shale/mud rock and he ran a sample through the X-Ray Powder Diffractometer and the gizmo spit out a bunch of squiggly lines on paper and he then was able to help with identification.  In other words, I don’t know much about the identification clay minerals.  But one clay mineral I did come to recognize was bentonite since the extensive oil industry in western Kansas used bentonite in their drilling muds.  These muds are used to keep the drill bit cool, bring drill cuttings to the surface for examination, and keep formation fluids from entering the drill stem.  I recognized it as bentonite since the sack containing dry clay said “bentonite.”  Bentonite is also scattered around in the Cretaceous rock exposures in western Kansas as altered volcanic ash.  During the Cretaceous, volcanoes to the west spewed out voluminous amounts of ash that settled into the marine waters of the Western Interior Seaway and slowly settled to the floor and accumulated in layers.  These layers are quite useful to stratigraphers since each layer (ranging in thickness from millimeters to tens of centimeters) has a unique chemical signature and can be traced over hundreds of square mines (chronostratigraphic units). 

 

Imagine my surprise when I opened the mount box and discovered that not all clay minerals, including palygorskite, are dull, clay-like fragments where crystals are not visible. The Michigan specimen is composed of lath shaped crystals bundled together in thin sheets in which the individual fibers are not visible with ordinary light microscopes. I immediately grabbed my Mineralogy of Michigan book (Heinrich revised by Robinson, 2004) and zipped to the palygorskite entry expecting to learn much about a mineral that I knew little about. Surprise! What I found was palygorskite is “a relatively uncommon fibrous mineral...Reported by Morris at the Ohio mines…near Michigamme.”   

 

Palygorkskite from Michigan.  Width FOV ~9 mm.

 

Palygorskite [(Mg,Al)₂Si₄O₁₀(OH)-4H₂O] is a  hydrated magnesium aluminum (sometimes the magnesium partially replaced by iron) phyllosilicate (sheet-like silicates; examples mica minerals, clay minerals) that has an earthy luster with pastel colors—white, gray, gray-green, brown-white, yellow.  It is quite soft at ~2.0 (Mohs).

 

Palygorskite is an interesting mineral due to its large number of depositional modes.  Authigenic palygorskite is formed by direct precipitation from solution, or from the development of the mineral by transformation of precursor minerals.  The direct precipitation process implies that a new mineral structure crystallizes, so that any prior mineral structure is not inherited. The latter process usually includes the dissolution of the precursor minerals (no inherited mineral structure) and then precipitation. With palygorskite one formation model indicates the mineral originates from aluminous precursors while a second model points to palygorskite as a result of direct precipitation from solution.  (above information from Pozo and Calvo, 2018).

 

So, what environments produce palygorskite?  It is common for magnesium clays to form in evaporitic depositional environments from aluminum detrital precursors (probably other aluminum-rich clay minerals) and are important constituents of weathering profiles and soils developed in basic and ultrabasic rocks, especially in arid and semi-arid climates (Pozo and Calvo, 2018), for example, evaporites in Senegal and Iran.

 

Thiry and Pletsch (2011) noted how palygorskite clays have developed in deep oceans at various times in geological history but especially in the Middle Cretaceous Atlantic. These authigenic clays formed when hypersaline bottom waters had similar chemistry as continental evaporitic environments.  These minerals seem to be the result of direct precipitation by transformation of inherited mg-rich clay minerals on the seafloor.

 

Xie and others (2013) described the pedogenic formation of authigenic palygorskite in the Red Loess Plateau in China (in other words relating to soil).  Here palygorskite forms: 1) from the weathering of preexisting smectite (a clay mineral); and 2) by a direct dolomite precipitation from pore fluids, associated with dolomite (magnesium calcite carbonate) crystallization. Palygorskite is a response mineral to change of climate and soil environment. 

 

The largest deposit of palygorskite in the United States is located along a trend extending from Meigs, Georgia, to Quincy, Florida.  Here the mineral formed in brackish water lagoons and tidal environments associated with a marine channel extending through southern Georgia (today’s geography) connecting the Gulf of Mexico with the Atlantic Ocean. The channel was bordered on the south by the “island of Florida.” This arrangement ended when the “Florida island” became connected to the mainland in the Miocene.  It appears that palygorskite found in Early Miocene sediments/sedimentary rocks is the result of alteration of the clay mineral montmorillonite (Weaver and Beck, 1977).

 

But what about my specimen of palygorskite collected from Precambrian iron rocks?  That is a really great question, and I have few answers.  Almost all palygorskite seems associated with sedimentary environments of some sort, both continental and marine.  However, there are two localities in Michigan that have produced palygorskite in a Precambrian iron mine environment: 1) the Imperial and Webster Mines (AKA Ohio Mines) in Baraga County; and 2) the Wakefield iron pit in Gogebic County.  Both of these areas are in the Upper Peninsula (Yooper Land).  

 

The Ohio Mine produced iron from both underground (Imperial) and surface (Webster) workings.  The pay zone was  the ~1.85 Ga  Bijiki Iron Formation Member of the Michigamme Formation which accumulated near the end of the Earth's initial phosphogenic episode (~2.2 and 1.8 Ga). It seems likely that the iron minerals of the Bijiki  precipitated out of surface waters and settled into a low-energy environment below wave base. It is fine grained, thin bedded, and cherty and contains black slate, varicolored argillite-siltstone, iron carbonate, and iron oxides.  The iron has usually weather to hematite and goethite and has been mined for iron ore (Ojakankas, 1994).

 

After about three days of looking through articles and maps I cannot locate information about the formation of the rare palygorskite. It is obviously a secondary mineral but when did it accumulate?  Where did it come from?  What was the depositional environment?   I don’t have the slightest idea!  Possibilities include 1) weathering of the precursor clay mineral smectite; 2) some association with Mg-rich brines associated with layered basalts; 3) precipitation with the iron minerals in a low-energy environment below wave base; or a really wild one; 4) on a tidal flat.  I got that idea from a couple of different sources.  A web site, The Diggings (www.thediggings.com) noted that in 1933 Ford Motor Company and E. A. Wetmore shipped out high phosphorus ore from the Imperial Mines. Hiat and others (2015) described a tidal flat containing phosphorus from the 1.85 Ga Michigamme Formation.  No mention of palygorskite but the tidal flat rocks could have been the source rock.  Wild guess since I am not a geochemist or mineralogist but an ole guy trying to learn! But then again since it is a secondary mineral and perhaps it formed much later than deposition/formation of the host iron rocks.

 

The palygorskite mined in Georgia is usually combined with smectite (a group of clay minerals commonly known as bentonite) and locally are known as attapulgite clays, and have important industrial uses: drilling muds, animal food, paints, tape-joint suspensions, wild fire suppressants, and a number of other uses. At one time it was used as an anti-diarrheal medicine such as Kaopectate ™.  In the Mesoamerican Mayan civilization palygorskite was use as a paint/textile pigment called Maya blue.

 

Sepiolite [Mg₄(Si₆O₁₅)(OH)₂-6H₂O] is a hydrated magnesium phyllosilicate that has an earthy, dull luster with pastel colors—white, gray, gray-green, brown-white, yellow.  It is quite soft at ~2.0 (Mohs) when fresh but hardens with exposure and heat. In other words, it is very similar to palygorskite except it usually lacks the aluminum. One major difference is that sepiolite has “serpentine” as its precursor.

 

Fibrous acicular crystals of sepiolite from Mexico.  Width FOV ~8 mm.

There are two major forms of sepiolite: 1) the fibrous type, similar to palygorskite lathes, but sometimes matted together into larger “pieces” and is often called Mountain Leather; 2) consolidated nodular masses of earthy particulates.  The first type is a novelty mineral often found in rockhound collections (my specimen is from Mina Cerro de Mercado, Durango, Mexico). The nodules are much more interesting as the original name for sepiolate was meerschaum.  Now any male college student of the 1960s would recognize meerschaum as the bowl of a tobacco pipe (finally you understand about the photo at the top).  The bowl was carved by artisans, allowed to harden in the heat, and then attached to a “plastic” stem.  Preferably the pipe was filled with Cherry Blend tobacco and smoked in a coffee shop while dressed in a tweed sport coat with leather elbow patches. As an undergraduate student I had the pipe (the bowl was covered with leather) and carried the Cherry Blend tobacco.  However, that particular tobacco had a great aroma in an open room but tasted like crap (at least in my mouth).  So, I just sort of carried the pipe around in my shirt pocket trying to look cool.  Before heading out to have a frothy adult beverage I left the pipe behind as there were no coffee shops in western Kansas and the Horseshoe Lounge had a large population of oil field workers and cowpokes who preferred Red Man chaw, unfiltered Camels, and snus/snooze. It was fascinating, however, to visit a tobacco/pipe store and see all of the beautiful carved meerschaum pipes. 

 

Personally, this has been a fascinating research project and I learned much.  It also reinforced thoughts that to even partially understand clay minerals: 1) one must have access to a XRD (Xray Diffraction) and/or SEM (Scanning Electron Microscope); and 2) have a good/great understanding of chemistry.  Guess that sorts of leaves me out! 

 

I apologize for all of the geology jargon in this post--it did not start out that way.  Sometimes minerals just need much explanation for me to understand.  This is one of those times!

Writing blog posts is like capturing birds without killing them. Sometimes you end up with nothing but a mouthful of feathers.                    apologies to Tom Waits

REFERENCES CITED

Heinricj, E.W., updated and revised by George W. Robison, 2004, Mineralogy of Michigan: A.E. Seaman Mineral Museum, Houghton Michigan.

Hiatt, E. E., P. K. Pufahl,  C.T. Edwards, 2015, Sedimentary phosphate and associated fossil bacteria in a Paleoproterozoic tidal flat in the 1.85 Ga Michigamme Formation, Michigan, USA: Sedimentary Geology, vol. 319.

Ojakankas, R.W., 1994, Sedimentology and provenance of the Early Proterozoic Michigamme Formation and Goodrich Quartzite, northern Michigan, regional stratigraphic implications and suggested correlations: United States Geological Survey, Bulletin 1904-R.

Pozo, M, andJ.P. Calvo, 2018, An overview of authigenic magnesian clays: Minerals vol. 8, no. 11.

Qiaoqin Xie, Tianhu Chen, Hui Zhoua, Xiaochun Xua, Huifang Xu, Junfeng Jic, Huayu Lu, William Balsame, 2013, Mechanism of palygorskite formation in the Red Clay Formation on the Chinese Loess Plateau, northwest China: Geoderma, vol. 192.

Thiry, M., T. Pletsch, 2011, Developments in palygorskite-sepiolite research in Developments in Clay Science, Elsevier B.D.

Weaver, C.E. and K.C. Beck, 1977, Mioceneof the S.E. United States: a model for chemical sedimentation in a peri-marine environment: Sedimentary Geology: vol. 17, issue 1-2.