Thursday, February 23, 2017


Submillimeter yellow "scales" of volborthite partially covering matrix.  Width of specimen ~3.6 cm.
In previous postings I have often written about the vanadates, along with the phosphates and arsenates, where vanadium bonds with oxygen to form a radical, VO4, with a charge of minus 3: (VO4)- - -  .  This anion then combines with metals or semi metals to form minerals.  And at times, PO4 and As4 substitute for the VO4.  However, vanadium also occurs in minerals where it acts as a cation with a plus 5 (usually) charge, V+++++.  One such mineral in this group is volborthite, a hydrated copper vanadate hydroxide [Cu3V2O7(OH)2—2H2O].

I have a couple of specimens purchase several years ago before Ackley’s Minerals, a small shop here in Colorado Springs, closed as the proprietors “retired” to the farm north of town.  Volborthite is a rare mineral that usually is observed as small, yellow to yellow-green “scales” encrusting part of a rock’s matrix.  The luster ranges from vitreous to opaque but is usually classifies as pearly.  The “scales” often may be seen as individuals but many times they are stacked on one another, and without magnification, appear as massive encrustations. On some specimens, but not mine, the small plates of volborthite form clusters of rosettes. The hardness is ~3.5 (Mohs) and I was able to get a light to pale green streak.  Volborthite does not fluoresce under a UV light.
Photomicrograph of volborthite "scales."  Width of photo ~6 mm.

Above two photomicrographs show submillimeter "scales" of volborthite.  
Volborthite is usually found in the highly-oxidized zone where hydrothermal solutions (coming off hot bodies of intruded magma) have deposited other vanadium-bearing minerals.  In the Colorado Plateau Type deposits, a sandstone-hosted mineral deposit, vanadium minerals often occur with uranium minerals; therefore, rockhounds originally believed minerals like volborthite were radioactive (just the radioactivity coming off the uranium minerals).  But, vanadium is a critical component of some uranium minerals such as carnotite: K2(UO2)2(VO4)2--3H2O.

Karpenkoite [Co3V2O7(OH)2—2H2O] is the cobalt analogue of volborthite since cobalt substitutes for the copper.  Martyite is the zinc analogue when zinc replaces the copper [Zn3V2O7(OH)2—2H2O].  Engelhauptite has the water (H2O) molecules replaced by potassium and chlorine molecules [KCu3(V2O7)(OH)2Cl].

My two specimens came from the Copper Hill Mine, Picuris District, Taos County, New Mexico, and according to the rock shop proprietors, were collected decades ago.  The Picuris District is part of the Sangre de Cristo Mountains and “is best known for the Harding pegmatite, a Proterozoic [late Precambrian] complex-zoned pegmatite, which has produced substantial amounts of beryl, lepidolite, spodumene, and tantalum-niobium (microlite) minerals” (McLemore and Mullen, 2004).  However, the Copper Hill Mine is a “strata-bound” copper-silver-antimony deposit” (Williams and Bauer, 1995) that produced the volborthite specimens.

I have been unable to locate much information about volborthite from the Copper Hill Mine.  In fact, MinDat does not list a primary vanadium mineral from Copper Hill; therefore, I “do not know” (no surprise here) where the vanadium “came from”?

McLemore, V.T., and K.E. Mullen, 2004, Mineral Resources in Taos County, New Mexico in New Mexico Geological Society Guidebook. 55th Field Conference, Geology of the Taos Region.

Williams, M.L., and P.W. Bauer, 1995, The Copper Hill Cu-Ag-Sb Deposit, Picuris Range, New Mexico: retrograde mineralization in a brittle-duct trap: Economic Geology, v. 90.

Monday, February 6, 2017


The vanadates are among my favorite group of minerals, and along with the phosphates and arsenates, are usually grouped and studied together.  In these three groups, arsenic (As) or phosphorous (P) or vanadium (V) combine with oxygen (O) to from the arsenate (AsO4), phosphate (PO4) and vanadate (VO4) radicals.  Each of these radicals, with a negative charge of 3-  then combines with a positive charged cation metal(s), and often with water (H2O) or hydroxide (OH), to form a wide variety of minerals.  Since the three radicals are approximately the same size they often substitute for one another in a solid solution series.  For example, pyromorphite [lead phosphate [Pb5(PO4)3Cl] is in solid solution with mimetite [lead arsenate Pb5(AsO4)3Cl]---the negatively charged radicals change.  The latter mineral is usually a pale yellow to yellow-brown color while pyromorphite is usually green to yellow-green in color; however, intermediate stages in the solid solution series are known (from work with XRD or EDS or other gizmos).  Each of these radical groups may also combine with a variety of metals (cations with a positive charge) that often form solid solution series with each other.  For example, erythrite [cobalt arsenate] is in a complete solid solution series with annabergite [nickel arsenate] as the cobalt cation substitutes for the nickel cation: Co3(AsO4)2-8(H20) to Ni3(AsO4)2-8(H20). Therefore, it is easy to understand the wide range, number and variety of arsenate, phosphate and vanadate minerals when so many combinations of cations and radicals are possible.

Many arsenate—phosphate—vanadate minerals are bright in color, have easily observable crystals and are widely available at mineral shows.  Therefore, I am a sucker, actually a buyer, whenever these minerals are located at shows (if the price is right)! 

The arsenates and the phosphates are well known minerals such as copper arsenates: olivenite and clinoclase and cornwallite; and copper, zinc arsenate: austinite; cobalt arsenate: erythrite; lead arsenate: mimetite; and nickel arsenate: annabergite.  The phosphates include such minerals as calcium phosphate: apatite group; lead phosphate: pyromorphite; lithium phosphate: triphylite and amblygonite; copper aluminum phosphate: turquoise; and the rare-earth phosphates: monazite and xenotime.
The vanadates are not nearly as well know, or as common, as the previous groups but do include carnotite, a uranium vanadate; mottramite and descloizite, copper-rich and zinc-rich vanadates forming a solid solution series; and the best known of the group, vanadinite, the red to orange lead mineral with beautiful and collectible hexagonal crystals.

At the 2016 Tucson Show I was rummaging through some minerals at Shannon and Sons toward closing time and came upon a specimen of pottsite.  Normally I would have known little about this strange mineral except I had been reading about minerals containing bismuth (Bi).  Pottsite is a quite rare hydrated (H2O) lead and bismuth vanadate [(Pb3Bi)Bi(VO4)4-H2O] found in the oxide zones of tungsten-bearing rocks.  MinDat noted that pottsite is the only natural lead-bismuth vanadate known.  The Pb/Bi ratio varies from0.86 to 1.48. At the rock and mineral shows that I frequent pottsite is not a common mineral for sale as the mineral has only been found in four localities (MinDat): Cordoba, Argentina; Bavaria, Germany; and Nevada, USA (Churchill and Lander counties).  It seems as most of the collected specimens come from the type locality, the Linka (AKA Garnetite) Mine, Spencer Hot Springs District in Lander County.  The major target at the Linka was tungsten with slight recovery of copper and molybdenum.  Sherlock and others (1996) defined the Spencer Hot Springs District as a “Tungsten Skarn” where scheelite-bearing [calcium tungstate], calc-silicate rocks are formed at boundaries of hot magma bodies (a granodiorite at Linka) and carbonate rocks.  The hot fluids dissolve some of the carbonate rocks (a process of metamorphism called metasomatism) and deposit a wide variety of minerals dependent upon the composition of the hydrothermal fluid.  Evidently at the Spencer Hots Springs District, tungsten was a major component of the fluids along with secondary? lead, vanadium and bismuth.  I remain uncertain as to the rareness of combining lead and bismuth.
Macro photograph  showing crust of yellow microscopic crystals of pottsite.  Width of specimen ~1.5 cm.
Pottsite occurs as a bright yellow, almost druse, of microscopic (usually submillimeter) prismatic crystals (Tetragonal), or as stubby prisms or bipyramids.  They appear to be translucent to transparent and are soft at ~3.5 (Mohs). 

All of the above are photomicrographs showing submilimeter prismatic to stubby crystals of yellow pottsite. I am simply uncertain about the globular orange minerals. the chalky white mineral may be bismutite that lost the copper component?  These were also the best enlargements that I could produce with my equipment. 
The mineralization process concluding with the formation of pottsite is a complex sequence of events.  Williams (1988), in describing this new mineral, pointed out:  Pottsite is a product of oxidation that followed these events [late metamorphism]. Junoite [copper lead bismuth sulfide] was first replaced by waxy green Bismutite [bismuth carbonate] streaked with grey cerussite [lead carbonate]; the green bismutite then lost copper and became chalky white. Typically the bismutite was then converted to a powdery orange (unknown) bismuth vanadate which, in turn was replaced by clinobisvanite [bismuth vanadate]. Sparkling crusts of this mineral are commonplace in fractures anywhere close to oxidized junoite. In a few spots pottsite has replaced the unknown bismuth vanadate instead of clinobisvanite. It does not occur in association with clinobisvanite.
I originally thought that perhaps some orange material in the small sample was clinobisvanite (BiVO4).  However, I could not locate any fluorescence in the specimen---any indicator of clinobisvanite.  I also remain somewhat confused (not all that difficult) with the statement by Williams (1988): It [pottsite] does not occur in association with clinobisvanite.  My confusion relates to photos on MinDat showing specimens with both minerals present.  Perhaps new studies since 1988 have shown both minerals may be found together?  One of life’s persistent questions!

Speaking of those questions:  Life’s most persistent and urgent question is “What are you doing for others?”
                             Martin Luther King, Jr.


Sherlock, M.G., D.P. Cox, and D.F. Huber, 1996, Known mineral deposits and occurrences in Nevada: in Chapter 10 from Nevada Bureau of Mines and Geology Open-File Report 96-2: An analysis of Nevada's metal-bearing mineral resources):

Williams, S.A., 1988, Pottsite, a new vanadate from Lander County, Nevada: Mineralogical Magazine, v. 52.

Friday, February 3, 2017


In wandering through my collection of minerals brought home from the 2016 Tucson Show, I came across a specimen of emmonsite.  I reached to the back recesses of my mind trying to remember why I purchased such a specimen.  Yes, it is a nice green-yellow color and looked interesting under the loupe but then I remembered—I was going to check and see if emmonsite was named for the famous geologist Samuel Franklin Emmons.  Well, I finally got around to checking and sure enough emmonsite [Fe2(TeO3)3-2H2O], a fairly rare iron (ferric) tellurite, was named for a well-known geologist that Colorado has sort of claimed as a native son (although he was born in Boston in 1841 and descended from a long line of native Bostonians—lineages arrived in the 1630s), or at least a favorite son.
S.F. Emmons, ca. 1860s.  Photo courtesy of Library of Congress.
The following information is abstracted and interpreted from Hague (1912) who wrote a “Biographical Memoir” of Emmons published by the National Academy of Sciences.  Emmons was one of those “old fashioned” geologists, attending private primary and secondary schools in Boston and finishing up at the Dixwell Latin School.  Emmons was educated to become a gentleman of broad culture, refined manners, and to enter Harvard University, which he did at age 17, and graduated in 1861.  When I first read “1861” I wondered why he did not enlist in the U.S Army since Harvard furnished a number of students to the anti-slavery movement.  Hague (1912) noted that Emmons’ father persuaded him to pursue a professional career, rather than to follow many classmates into military service.  To further discourage enlistment (I presume), Emmons was sent by his father, after graduation, to Europe in order to accompany his mother on a health recuperation trip.  He seemed to have spent the summer of 1861 climbing mountains and hiking, and presumably taking care of his mother.  She sailed back to the States in November while Emmons toured London and ended the year in Paris.  In the City of Eternal Light, Emmons spent nine months working under private tutors in order to relearn French and prepare for entrance exams to the prestigious Ecole Imperiale des  Mines  (School of Mines).  Emmons spent two years at the School of Mines and then decided he wanted to get a more practical mining experience (hands-on) so spent the next year (1865) at the Bergakademie (Mountain Academy) at Freiberg, Saxony, Germany (where there were mines at the city limits).   After leaving Freiberg, Emmons spent the winter in Italy and finally returned to Boston in June 1866 (probably to the delight of his family since the conflict was over).
As a graduate student at the University of Utah, I fell “in love” with reading about the geological exploration of the American West via the Great Surveys:  F.V. Hayden and the United States Geological Survey of the Territories; Clarence King and the Geological Exploration of the Fortieth Parallel; John Wesley Powell and The Exploration of the Colorado River and its Canyons; George M. Wheeler and the many volumes of Explorations and Surveys West of the 100th Meridian.  These surveys of the western United States ultimately were reorganized (1879) into the United States Geological Survey.
A "Great Surveys" volume picked up at a garage sale 50 years ago.
This was an exciting time to be at the University since the senior instructors were only a couple or three generations removed from the early western geologists and had traversed the wide-open spaces of the west when it was still “wild.”  They had been trained as classical geologists (mostly in the eastern U.S.)  and tried to impart their thoughts to the students, especially the need for precise field work.  Our field trips often were taken to areas touched by Great Surveys.  I sort of fell into a trance standing at the entrance to Ladore Canyon on the Green River trying to imagine what John Wesley Powell felt as he guided his small boats into the “great unknown.”  Students were greatly impressed with the detective work of Clarence King (including Emmons) and his geologists in debunking the great diamond find in northwestern Colorado and we wondered if a ruby or diamond still were to be found?  Alas, no luck.
But back to Emmons (following Hague, 1912).  Upon returning to the States Emmons secured a job, at first as an unpaid volunteer, with the King Survey and they sailed for California in May 1867. He later was hired as an assistant geologist and Hague (1912) noted that Emmons “was full of youthful spirits and manly exhilaration over the work before us.”   Emmons worked for 10 years with various aspects of the King Survey that perhaps culminated with the publication (890 pages) of descriptive geology.  I did not realize (no surprise here) that after leaving the Survey Emmons “engaged actively in cattle ranching, and for some time made his home in Cheyenne, Wyoming.”
In 1879, the U.S. Congress created the Bureau of the Geological Survey (the USGS) and Clarence King was appointed the first director on April 3.  On August 4 of that year King appointed Emmons as “Geologist in Charge of the Rocky Mountain Division” and a mandate to devote his first years to “a study of the mineral wealth of the Rocky Mountains.”  In 1886, Emmons was the lead author of USGS Monograph XII, Geology and Mining Industry of Leadville, Colorado with Atlas (~779 pages).  Hague (1912) noted that it “won for its author an international reputation…probably no single publication of the geological survey has exerted a more beneficial influence and stimulated more discussion.”  Professional geologists could ask for little more than an accolade like that.
After Leadville Emmons lead an active geological life with an amazing number of papers on a wide variety of subjects, including: On glaciers in the Rocky Mountains; Notes on gold deposits in Montgomery, County, Maryland; Geology of the Tintic Special District, Utah.  In Colorado Emmons is remembered for excellent papers on Colorado ore deposits, Geology of Aspen Mining District, Geology of the Elk Mountains, Geology of Rosita and Silver Cliff and Mines of Custer County, Geology of the Denver Basin, and Geology of the Ten Mile District.  I would encourage interested readers to observe his bibliography (Hague, 1912) found at:  In addition to his publications, Emmons was one of the founding members of the Geological Society of America and served as the President in 1903.
Also of interest to Colorado scientists: (in the history of the Colorado Scientific Society, the oldest scientific society in the Rocky Mountain region at   On the evening of December 8th, 1882, a number of gentlemen interested in the formation of a scientific association met in the rooms of the United States Geological Survey, in Denver, at the invitation of Mr. Samuel Franklin Emmons.” “Mr. Emmons, in stating the object of the meeting, said that it seemed to him that the time had come for those persons in Colorado who were interested in true science to unite in forming an association or society, whose immediate object would be to facilitate the interchange of scientific observations and ideas, and promote intercourse among the observers themselves. There should be some means of recording and publishing the many interesting and valuable facts which are daily observed in different parts of the State. This could be done through the medium of a society, and the opportunity thus afforded would no doubt act as a stimulus to some to pursue investigations in directions specially open to them.” “An informal discussion ensued in which the advisability of such a step was advocated, and it was agreed to proceed at once to form a permanent organization.” “The following named persons were unanimously chosen as officers for the first year: President—Samuel Franklin Emmons Vice-President—Richard Pearce Secretary—Whitman Cross.”
Although Emmons was not a “Native Coloradoan” his work certainly qualified him as perhaps the most respected geologist in in the state’s history.  Emmons was active until his death in 1911.  Hague (1912) noted that “he left a noble record of life’s work well performed.”
Among other honors bestowed on Emmons, Colorado designated a 12,401-foot peak near Crested Butte in the West Elk Mountains as Mt. Emmons.  Not to be outdone, Utah designated a 13,448-foot peak in the High Uintas Wilderness as Mt. Emmons.  Interestingly, the Utah peak is connected by a rugged ridge to the highest peak in Utah, Kings Peak at 13,534 feet.  So, even in death Emmons and his long-time friend and colleage, Clarence King, remain connected.
Mt. Emmons, Colorado, 12,401 feet.  Photo courtesy Google Earth.
Mt. Emmons, Utah, 13,448 feet.  Photo courtesy Google Earth.
This offering started out about the mineral emmonsite and so it will finish with the same.  Emmonsite is one of a few minerals that contain the element tellurium, a silver-white metalloid (possesses properties of both metals and non-metals). Tellurium is an extremely rare element as most rocks contain about 3 parts per billion and is 8 times less abundant than gold (Goldfarb, 2014), and is related to selenium but may be only mildly toxic!  Tellurium is rarely found in a native form.
Tellurium can act as a cation with a +2 valance as in the uncommon mineral tellurite, TeO2, or with a +6 valence as in jensenite, Cu3TeO6-2H2O   The telluride anion with a charge of -2 can combine with gold and silver cations in the minerals calaverite (AuTe2) and sylvanite (AuAgTe4).  These telluride minerals form major gold ores at Cripple Creek, Colorado.  So, it is confusing when one talks about tellurium, tellurite, and telluride.
Emmonsite [Fe2+++(Te++++O3)3-2H2O; a hydrated iron tellurite, occurs in a wide variety of habits from microscopic druses, to hair-like masses, sprays, compact masses, globs, and small acicular crystals.  I could not locate information on larger than microscopic crystals but MinDat lists emmonsite as belonging to the Triclinic System. It has a green to yellow-green color, vitreous to subvitreous to even dull luster, opaque to translucent to transparent diaphaneity, and is reasonably hard at ~5.0 (Mohs).  Its characteristic yellow-green color combined with the often branching (coral-like) or fungus-like shape are the best identifying marks.  Emmonsite is a secondary mineral found in the oxide zones of hydrothermal tellurium-bearing base minerals.  It is often found with native tellurium and the telluride minerals.
Green, fungal-like habit of emmonsite.  Length main "mass" of mineral ~4 mm.
Hillebrand (1885) gave the type locality of emmonsite as Tombstone, Arizona. As described by Pearl (1941), the discovery of a new mineral which he named emmonsite in honor of Samuel B. Emmons, first president of the Colorado Scientific Society and one of America's outstanding geologists, was told by W. F. Hillebrand at the meeting of the society at the Arapahoe County (now Denver) Court House on June 1, 1885. The mineral had been sent by R. C. Hills from an uncertain locality near Tombstone, Arizona Territory. So, it would seem that Emmons was (may have been) at the Colorado Scientific Society meeting when Hillebrand gave his description of emmonsite.
Hillebrand (1904) also described emmonsite(?) from Colorado and in Bulletin 262 of the USGS (1905) stated a green mineral was collected at the W.P.H. Mine at Cripple Creek that showed a close resemblance to emmonsite he described 20 years ago (the specimen from Tombstone).  However, Williams (1980) believed that the mineral described from Tombstone actually was rodalquilarite, a hydrogen iron tellurite chloride.  Eckel and others (1997) then believed it would then make sense to declare the mines at Cripple Creek, Colorado, as the type locality for emmonsite.  However, I note that MinDat still lists Tombstone as the type locality.
My specimen of emmonsite was collected from the Bambolla Mine (Montezuma Mine) located in Municipio de Moctezuma, Sonora, Mexico.  I have been unable to locate much information on the Mine other than in the 1970s, it was a producing gold mine.  I assume, that like nearby mines, mineralization was related to hydrothermal activity associated with Tertiary volcanic action.  However, the amazing information is that the Mine, and the nearby (half mile away) Bambollita Mine, are the type localities of at least 23 tellurium-bearing minerals!  Also, I stumbled upon an article, actually a discussion, of a micro-mineral group (Associazione Micro-mineralogica Italiana).  Luckily, the discussion was in English!  At any rate, Ciriotti (2010) noted: Oxide-zone tellurium minerals are relatively rare worldwide… 71 known Te-oxide minerals, 68 of which are considered valid species; most are either tellurite (Te4+O3)2- or tellurate (Te6+O6)6- species… over 60% of the species (43 out of 71) were discovered at only four deposits: Moctezuma, Mexico; Tombstone, Arizona; Centennial Eureka Mine, Utah; and Otto Mountain, California. In fact, nearly a third of all Te-O mineral species were discovered in just one deposit: Moctezuma. Many of these species are still found at only one locality today… The four leading occurrences listed above are all oxidized base metal deposits, and not surprisingly, 60% of all Te-O minerals contain Pb and/or Cu. If Zn and Fe are added in, this increases to 84%... And that sort of sums up my limited knowledge about tellurium minerals.

This is one of those postings that started out as a simple discussion of the Colorado Scientific Society and its first president S. F. Emmons.  However, it morphed into the fascinating world of tellurium and the resulting minerals.  I am still trying to digest some of the information but needed to draw a conclusion line---somewhere!  Unfortunately, the length and breadth of the subject may turn off all but the most dedicated readers and for this I apologize.  But, just as a dog worries a bone I worry a subject that I don’t really understand.  The good thing is that “new learning” is a joy for me and hopefully keeps my brain alive. My philosophy about learning may be summed up by two rather famous individuals:

Anyone who stops learning is old, whether at twenty or eighty.  Anyone who keeps learning stays young.   Henry Ford

Every time I learn something new it pushes some old stuff out of my brain.    Homer Simpson

Ciriotti, M.E., 2010, Oxidation zone tellurium minerals: Associazione Micro-mineralogica Italiana.
Eckel,E.B. (and others), 1997, Minerals of Colorado: Denver, Fulcrum Publishing.
Goldfarb, R., 2014, Tellurium—the bright future of solar energy: USGS Fact Sheet 2014-3077.
Hague, A., 1912, Biographical memoir of Samuel Franklin Emmons, 1841-1911: National Academy of Sciences, Biographical Memoirs, v. VII. 
Hillebrand, W.F., 1885, Emmonsite, a ferric tellurite: Colorado Scientific Society Proceedings, v. 2, pt. 1.
Hillebrand, W.F., 1904, Emmonsite(?) from a new locality: American Journal of Science, 4th Series, v. 18, no. 108.
Hillebrand, 1905, Two tellurium minerals from Colorado: U.S. geological Survey Bulletin 262. 
Pearl, R.M., 1941, Minerals named for Colorado men: Colorado Magazine, v. 18, no. 2.

Williams, S.A., 1980, The Tombstone district, Cochise County, Arizona: Mineralogical Record, v. 11, no. 4.

Monday, January 23, 2017


Today, in the middle of Kansas, is a small town with a population of “around” 400 persons and maybe a hundred more if one counts free-range dogs.  I left the town ~55 years ago when the population was about 400 people plus the dogs.  It was a pretty "normal" farming community where a “typical farm” ranged from a section quarter to perhaps an entire section.  Larger acreages usually included some land rented by the farmer.  In addition, each farm usually raised a few head of livestock—hogs, cattle, chickens—for sale and for personal use.  Dogs abounded as did the free-range cats that were called “mousers.”  The cats were “just there” and were often quite wild.  In addition, because of inbreeding there were several of these animals that were not the sharpest pencil in the box!
Free-range dogs appreciate attention, especially after a long hike.  The broken clavicle?  Just a little friendly wrestling match!
I distinctly remember Saturday evenings when the outlying occupants came into to town for the weekly “trading” (as my mother called it) at the two grocery stores.  The trading was usually in the form of chicken eggs that a farmer might bring in and “trade” for a few groceries.  My father operated a gasoline (plus the usual small scale mechanic work) station and rarely took in trades unless he figured out that commodities would be his only way to collect a debt.  One time we had enough butter to last a year, and to a small kid that staple was magic compared to the terrible tasting oleomargarine that usually stocked our pantry.

One of the great things about growing up in such a small town was the fact that kids were like the local dogs---free-range. We simply wandered all over town and had a boundary of about one mile in any rural direction to explore.  Just be home by supper.
Old friends after a tough day of hunting for turdites.  That Kansas sun can be hot so don't laugh at the hat!
I bring this up since I was a rockhound at an early age and always picked up and hauled home anything that caught my eye.  But, I also named many of these special rocks—nothing serious since I didn’t have the slightest idea what they really were.  Therefore, my names were like crickite (we pronounced the streams cricks) for finding the stone in a creek, roundyites (shape), slaberoos due to the layering, and turdites, a young boy’s favorite rock name (giggle, giggle), etc.  The names I conjured up generally were due to either shape or location.  Today, I suppose most new mineral names come from honoring a person.  However, one mineral I could have named as a child is the sulfosalt cylindrite (FePb3Sn4Sb2S14).  What appears as crystals in cylindrite specimens are actually rolled up flat sheets in the form of a cylinder, kind of like rolled tobacco leaves in a cigar.  Unfortunately, I never had a chance to collect the mineral as most specimens come from Bolivia.
Massive cylindrite mixed with the typical rolled-up sheets.  Longest cylinder in center is ~1.1 cm.
Photomicrograph (black & white) of above specimen.  The shiny metallic luster does not work well with my scope. Again, the longest cylinder is ~1.1 cm.
Cylindrite belongs to the sulfosalt minerals, a member of the sulfides group.  Sulfosalts contain a metal (mostly lead, copper, iron or silver although a few others, mercury, zinc, vanadium may be present), a semi-metal like arsenic, germanium, bismuth, antimony, or the metals tin or vanadium, and then sulfur (Richards, 1999).  

Because of the interesting habit of cylindrite, I found a specimen last February at one of the Tucson dealers (Shannon and Sons Minerals). The mineral is black to dark gray in color with a metallic luster.  It is quite soft at ~2.5 (Mohs) and has the traditional opaque diaphaneity of metals and the malleable tenacity. Although cylindrite appears in massive or cylindrical forms, Triclinic crystals are present but tiny (beyond the limits of my microscope).  I really don’t understand the mechanism behind the formation of cylinders.  Evidently, cylindrite originally occurs as stacked and layered structures but these flat sheets begin to deform from pressure and “roll up” into smooth cylinders.  MinDat states that “layer curving is one of the ways of an accommodation of the dimensional sheet misfit by a cylindrite crystal.”  That is about all that I can understand!  However, I do note that several references refer to cylindrite rolls as crystals; however, the large rolls are not individual crystals but rolled up sheets and the sheets are composed of individual crystals.

Cylindrite is a fairly rare mineral and most specimens come from mines in Brazil; my specimen was collected from the Itos Mine, Oruro City.  There are several tin-silver mines in the area and some produce cylindrite.  The mineral seems to form as the result of hydrothermal solution next to an igneous intrusion. For reasons beyond my comprehension, there are numerous studies that have been completed on synthesizing cylindrite and relatives (mainly franckeite).  During these studies microprobe analyses indicate there may be some solid solution series between lead and tin in cylindrite. I have read a number of these papers without really understanding much—see Jiuling and others, 1988.  I simply picked up my specimen due to the nifty habit of rolled up cylinders.

Can you imagine us years from today,
Sharing a parkbench quietly
How terribly strange to be seventy
Old friends, memory brushes the same years,
Silently sharing the same fears.
                             Simon and Garfunkel  

Jiuling, L., H. Jiashan, Z. Kezi and Z. Guilan, 1988,  An experimental study on three quaternary phases in the Fe-Sn-Sb-S System: Pb-free Franckeite, Pb-free Cylindrite and (Fe, Sb)-Ottemannite s.s.: Acta Geologica Sinica, v. 1, no. 4.

Richards, J.P., 1999, Encyclopedia of Geochemistry in Encyclopedia of Earth Sciences Series, C.P Marshall and R.W. Fairbridge, eds.: Springer Netherlands.