ADD SOME MAGNESIUM: GET A MOON ROCK

FIELD SPECIMEN OF TOPAZ-BEARING RHYOLITE FROM THOMAS RANGE, UTAH, WITH CRYSTALS OF PSEUDOBROOKITE.  ENLARGEMENTS BELOW.  WIDTH OF SPECIMEN ~7 CM.

Last fall I was pounding around on some rhyolite brought home from a 2010 field trip to the Thomas Range in western Utah (see April 3, 2011 posting).  A few members of CSMS had visited the Range in hopes of collecting topaz crystals (that was accomplished).  And, we also had aspirations of collecting giant red beryl (“bixbite”) specimens since this is one of the rarest and most expensive gemstones in the U S.  Current prices for good faceted stones range up to ~$10,000 caret.  Alas, Jerry found a few tiny hexagonal flakes (non-gemmy) and we were not to become wealthy.  But, even those tiny crystals are prized by collectors.  I picked up a single cube of bixbyite and later found a second specimen attached to a topaz crystal while sorting rocks at home.  Thus, last fall I dug out the rocks and thought perhaps a new bixbyite would show up or, never giving up hope, a crystal of red beryl.  But that was not to be.

In a serendipitous moment of breaking rocks, I did locate a few small crystals of pseudobrookite--- not a common mineral and an exciting discovery.  I noted to the field trip group back in 2010 that pseudobrookite might be present at the topaz diggings and so watch out for small sprays of black minerals.  In fact, that was about all that I knew about the mineral—it was dark colored, some sort of a titanium mineral, occurred in tiny needle-like crystals (often), and was not related to the mineral brookite.  I thought that amount of information was not too bad for an ole paleontologist!

So, in whapping the rhyolite I noticed some small dark minerals in the cavities and reached for my hand lens.  It appeared that the elusive pseudobrookite had been found and this discovery was confirmed when I examined the specimen under a binocular microscope.  Not quite red beryl, but good enough.

This finding piqued my interest in the mineral and I decided to learn a little more.  Not everything about aging is great but one of the “good things” is being able to study a subject in depth.  So, out came the mineral books and to my disappointment they were essentially void of information, or even recognizing the mineral existed!  However, the premier mineral site on the web, www.MinDat.com, came to the rescue and the following is abstracted from their site.

Pseudobrookite is an iron-titanium oxide, Fe₂TiO₅, and has both needle-like and tabular crystals.  I presume the name comes from its non-relationship with Brookite, a titanium oxide (TiO₂) mineral often with tabular crystals.  It does occur in colors other than “dark”, such as black, reddish-brown, and brownish-black.  The crystals have a hardness of 6 and a “shiny” (metallic or adamantine) luster (due to the titanium).  It usually occurs in younger volcanic rocks, especially rhyolite, in lithophysal (vugs caused by expanding gases) cavities.  According to Minerals of Colorado, pseudobrookite is found in the rocks at Ruby Mountain in Chafee County.  This seems reasonable since the Ruby Mountain rocks are mostly a topaz-bearing rhyolite.

Now, here is an interesting tidbit.  There is a solid solution series between pseudobrookite and armalcolite with magnesium substituting for part of the iron.  The “interesting” point behind this is that armalcolite, (MgFe²⁺)Ti₂O₅, was first identified from samples collected by Neil ARMstrong, Edwin ALdrin, and Michael COLins (Apollo 11) on the “Moon” at Tranquility Base.  Since then the mineral has been identified worldwide from several localities, including Utah, Wyoming, Montana and Texas.  Now, there is a fact for a trivia game!

mike 

CRYSTALS OF PSEUDOBROOKITE IN TOPAZ-BEARING RHYOLITE.  LONGEST INDIVIDUAL ~2 MM.

CRYSTALS OF PSEUDOBROOKITE IN TOPAZ-BEARING RHYOLITE.  LONGEST INDIVIDUAL ~4 MM.

WELCOME TO CHAOTIC FUN: QUARTZSITE, ARIZONA

PART OF THE FLEA MARKET, A WELL-MANAGED PART, WHERE VISITORS MAY PURCHASE, WELL JUST ABOUT ANYTHING INCLUDING RV WIND SOCKS. 

Quartzsite, Arizona is…….?  Well, I find it hard to describe the small desert community located near Exit 17 on I-10 in the far western part of the state.  Perhaps the best term is one used in a Phoenix newspaper—“chaotic fun”.  Somewhere in the neighborhood of a thousand hardy people stick out the summer months in town (the locals say it is hard to determine) where temperatures of 115 are common.  However, come January and February a million visitors descend to the area, mostly in RV’s of every type, shape, age, color and condition.  It sometimes looks like half the population of Minnesota is in town. The local RV parks are full, but the most amazing site is to examine the thousands of vehicles “dry camped” in the desert---no water, sewer, or electricity.  Just a weekly trip to town to “dump” and fill up the water tanks. 

Most vehicles sprout satellite dishes that provide a boob tube when the generator is cranked up.  The BLM manages the “La Posa Long Term Visitor Area” (camping) near town but many/most RV’s, tents, station wagons, vans, panel trucks, you name it, just head out in the desert.  It is a sight to behold.

Besides the warm January and February weather, visitors (“The largest gathering of Rv’ers in the world” according to a local web site) head to Quartzsite for the outdoor (tents and tables) rock, gem and mineral shows and perhaps the “world’s largest flea market”.  New venues added in recent years include hobby and craft shows, a classic car, and a sports and vacation show.     

Any rock hound will immediately recognize the name “Quartzsite” although he/she has never even seen the locality.  Visit almost any club meeting in the late fall and you will hear comments such as “going to Quartzsite this year”?  I’m heading down right after the first of the year”.  People with our interests drive and/or camp at Quartzsite to look at, and usually buy, rocks and minerals and lapidary supplies.  There are literally hundreds of vendors willing to supply a rock hound’s every need, especially during the “really big show’ in January.  As February begins many vendors, and some visitors, are on the way to Tucson.  However, the Desert Gardens rock show continues until the end of February.  By early March most vendors and visitors are pulling out for other parts.

I have visited Quartzsite a couple of times, but never in January.  My experience in February has been fairly high prices and big rocks.  It seems that many vendors in February are selling slabs and cutting material rather than mineral specimens.  Perhaps the specimen dealers moved on.  I also found prices to be, in my opinion, rather high.  Many of the rocks and gems could be purchased at a lower price in the numerous rock shops that I have visited.  And, most of the tools were comparable in price to the local hardware.  But then again, I am not a price negotiator, and have never adapted to that culture.

One place that did disturb me was a booth selling remnants of a cave.  It appears that workers had destroyed a cave and hauled out tons of drip stone, stalagmites, and stalactites.  A sad site.

But, the Quartzsite shows are am amazing place to visit and certainly “chaotic fun”.

mike

ROCKS ANYONE?  BARRELS AND BARRELS FOR SALE.

A 20 POUND PIECE OF ALABASTER FOR $80!

MAYBE AN 18 POUND SLAB OF PLAIN OLE BASALT FOR $36.

ARIZONA PERIDOT WAS A BARGAIN WITH A SMALL 15 POUNDER GOING FOR $45!

 

THE 79 MINE: AURICHALCITE

AURICHALCITE ON LIMONITE.  SPECIMEN ~26 mm.

The 79 Mine, Arizona, is a well-known mining area northeast of Tucson (north of the Hayden-Winkleman area) that has produced a wide variety of spectacular mineral specimens since its discovery in 1879.  MinDat (http://www.mindat.org/loc-3322.html) states: the underground mine formally produced lead, zinc, copper, gold, silver, molybdenum, antimony, vanadium and iron until the early 1950’s and mineral specimens until the 1990’s.  The oldest rock exposed in the Hayden area is the Proterozoic Precambrian Mescal Formation of the Apache Group.  Above this unit are several thousand feet of Paleozoic rocks (Cambrian to Pennsylvanian).  The major ore body is over 300 meters long and a dozen meters wide and occurs as replacements in the Naco Limestone (Pennsylvanian) and a dike of rhyolite porphyry. The mineralization is most likely Laramide (late Cretaceous and early Tertiary) in age. 

One of the “different” sort of mineral that is found at the 79 Mine is aurichalcite, a zinc copper carbonate hydroxide,  (Zn,Cu)₅(CO₃)₂(OH)_6. Aurichalcite is a secondary copper mineral that usually is found in alteration zones of large hydrothermal replacement bodies. Its friends seem to be azurite, malachite, smithsonite, and limonite. I consider it “different” since it occurs as very delicate, feathery acicular crystals only a few mm long.  The crystals run from pale green to blue-green to sky blue and are wonderful to examine under a scope or hand lens.

The specimen pictured here is from an old collection (I guess old is relative) procured in the 1970’s.  I purchased it at the Tucson 2012 show.

mike

PHOTOMICROGRAPH OF AURICHALCITE.

PHOTOMICROGRAPH OF AURICHALCITE ON LIMONITE. 

9th CIRCUIT COURT OF APPEALS

Last week a federal appeals court handed down an interesting decision: that the United States Forest Service could no longer charge auto parking fees for hikers (perhaps even rock hounds)  heading to certain trails in the Catalina Mountains near Tucson, AZ.

The 9^th Circuit Court of Appeals ruling could bring an end, or at least change the outlook, on fees gathered by the USFS to pay for improvements.  I am uncertain if the ruling applies only to the Catalina Mountains or to fees the USFS collects at numerous other locations (probably the latter).  As I understand it, the USFS has collected, since 1996, parking fees for hikers in some of the canyon areas of the Catalina’s. Since the hikers were not using improved facilities (campgrounds etc.), fees could not be charged.  

The court case is Adam et. al. v USFS.  Perhaps it will be appealed by USFS?  I would assume that a USFS ruling would also apply to lands managed by BLM, and perhaps other federal agencies. 

 

This case may have wide implications for recreation and other fees assessed by federal land managers.  But again, it may not!  I look forward to hearing about future results.

 

mike

 

 

COPPER RIVET MINE: COLORADO

VUG IN SANDSTONE COLLECTED AT COPPER RIVET MINE.  NOTE GEMMY CLEAR CALCITE PARTIALLY ENCRUSTED WITH GREEN MALACHITE AND BLUE AZURITE.  NOTE TINY GREEN ACICULAR CRYSTALS NEAR LOWER LEFT PART OF SPECIMEN. 

At the Tucson Electric Park/Kino Complex show I purchased an interesting specimen collected from the Copper Rivet Mine (uranium and copper) in Mesa County, Colorado, about 10 miles south of Gateway (Juanita Arch Quadrangle, 38.535ºN, 108.975ºW).  The seller indicated the specimens were collected in the early 1960's and that he had purchased a flat for resale; I immediately snapped up one!

Thus far I have not had access to an appropriate geological library to locate geological information.  However, the mine is very near the Utah-Colorado state line in an area of copper production; MinDat (www.mindat.org) noted that the Copper Rivet is located several miles north of the Cashin Mine.  The North Jeffco Gem and Mineral Club collected at the mine in a 2000 field trip that is described at peaktopeak.com/njeffco/2000/copperrivet/copper00_rep.php.  They described the hike to the dump and mine adit as 'strenuous".

The specimen, ~2.5 x 2.5 inches, has gemmy clear calcite crystals with coatings of boytrodal malachite and microcrystals of azurite appearing as "blobs".  And, there are quite tiny, green acicular crystals of what I am guessing is malachite although their green color is a different shade than the boytrodal form.  MinDat listed the following minerals known from the Copper Rivet: Azurite, Baryte, Bornite, Calcite, Chalcocite, Chalcopyrite, Luzonite, Malachite.

PHOTOMICROGRAPH OF SPECIMEN SHOWING BOYTRODAL MALACHITE (~2 MM), BLUE AZURITE, CLEAR CALCITE.

PHOTOMICROGRAPH OF SPECIMEN EMPHASIZING GREEN ACICULAR CRYSTALS.

KINO SPORTS COMPLEX SHOW 2012

VENDORS SELL WARES FROM RV'S OR TABLES.

The Tucson, Arizona, "rock show" is much more than the four-day main event, the Tucson Gem and Mineral Show, held at the Tucson Convention Center  The event this year will focus on "Arizona Minerals: so I expect to see, among other items, some really great specimens of azurite and wulfenite and malachite.  However, there are something like 40 total venues scattered throughout the city.  One of my favorite shows is the former Tucson Electric Park (TEP) Mineral and Gem Show now know as the Kino Sports Complex Rock Show.  This show, south of downtown along I-10, is set up on a series of soccer fields with free parking, free shuttles, and offers the opportunity for "dry camping" at $10 night.

The great thing about the Kino Show is, in my opinion,  the total lack of pretense among the vendors.  Sellers at one area come and park their RV's and sell items off tables and tarps, or perhaps from the bed of their pickup. There are the usual suspects such as Mt. Ida quartz, Moroccan trilobites, and agates from across the world.  However, a little searching and visiting with usually friendly vendors will often produce specimens of incredible beauty and perhaps a little scarcity.  One specimen of interest that I picked up was ~2.5 x 2.5 inch rock with encrustations of calcite, azurite and malachite collected from the Copper Rivet Mine in Mesa County, Colorado.  The vendor told me that he had purchased a flat of Copper Rivet specimens from a person liquidating their collection and that the minerals were picked up in the 1960's.  More on this specimen later.

At an adjacent field field vendors have set up GIANT tents and sell a variety of beads (10's of thousands), lapidary equipment, petrified wood, taxidermy mounts, hats, hundreds/thousands of amethyst cathedrals, and a variety of other funky items.  Some of the specimens were truly unique such as a hunk of schist about the size of a "Smart Car".  Or perhaps dyed amethyst cathedrals, or a two ton rock with a stain of blue copper material.

At any rate, the Kino Show is a great place to wander around for several hours, if for nothing else to observe more amethyst cathedrals than you have ever seen in one place. 
mike

COYOTE BONES FOR SALE?  WHY?

THIS SAW MAY BE WHAT CSMS NEEDS IN THE LAP SHOP!

ROCKS FOR SALE BUT A FLAT BED TRUCK IS NEEDED FOR HAULING.

.

THE OBLIGATORY CEPHALOPODS

BEADS ANYONE?

EVERYONE NEEDS AN AMETHYST CATHEDRAL.

PETRIFIED WOOD FROM INDONESIA.

BAKING NEW MEXICO SHALE

THE CRETACEOUS PIERRE SHALE INTRUDED BY A DIKE NEAR MP 435-436 ALONG I-25 IN NORTHERN NEW MEXICO.

The Raton Basin is a structural basin--beds dipping toward the center-- straddling the New Mexico-Colorado state line immediately east of the Rocky Mountain front.  The basin is asymmetrical with the basin axis closest to the bounding Sangre de Cristo Range on the west (steeper dipping beds).  The eastern boundary includes the Apishapa Arch and Las Animas Arch (Colorado) and Sierra Grande Arch or Uplands in New Mexico.  Tertiary sedimentary rocks are well exposed in the center of the Basin while the Cretaceous Pierre Shale often crops out along the exterior boundary.

The Basin is probably best known for 1) the dikes associated with the  Spanish Peaks granitic intrusives near Walsenburg, Colorado; 2) the coal mines and coal bed methane wells associated with the Cretaceous Vermejo Formation and the late Cretaceous-early Tertiary Raton Formation near Trinidad, Colorado; 3) the Miocene volcanic rocks capping the mesas at Raton Pass; and 4) exposures of the K-T boundary in the Raton, New Mexico, and Trinidad areas.

Most visitors to the Basin are impressed with the numerous radiating dikes near Walsenburg and La Veta, and they are correct.  These dikes are pictured in hundreds of textbooks and popular reading materials and are recognized by geologists the world over. 

However, the place to get “up close” to an igneous intrusive is to examine the smaller dikes cropping out, generally perpendicular to the basin axis, across the state line in New Mexico. Along I-25 near MP 436 and 435 (south of the city of Raton) the interstate cuts through two dikes and exposes their central core as well as the adjacent baked Pierre Shale.  The metamorphic aureole of the Pierre extends about 12-15 feet on either side of the dike.  The shale has been altered to a hornfel.  The age of the intrusion is either Eocene or Oligocene.

mike

 

GEOLOGIC MAP OF THE RATON BASIN, NEW MEXICO AND COLORADO.  MAP COURTESY OF USGS GEOLOGICAL SURVEY BULLETIN 2184-B. 

THE DIKE IS HARDER THAN THE SHALE AND THEREFORE IS MORE RESISTANT TO EROSION.  NOTE THE BAKED SHALE ADJACENT TO THE INTRUSION.