BLUE LAVENDULAN: TUCSON 2016

The Kino Gem and Mineral Show is one of the larger venues housing items for sale at the Tucson shows.  In 2016 there were 205 vendors listed; however, it seems increasing difficult to purchase individual mineral or rock specimens.  Instead there are a wide variety of somewhat bizarre items for sale including guns (this is Arizona), “coon skin” hats complete with tails, authentic animal fur and skins, incense, gongs and brass items direct from Asia    The tents are set up at the Kino Sports Complex in south Tucson and are a mixture of individual tents and the large football field size units.  One large unit houses dealers displaying a great variety of lapidary machines while another tent has smaller kiosks stocked with overpriced jewelry.  What is missing are the small mom and pop operations that were once the heart of the venue---essentially booted out.  But life goes on as buyers could locate a great variety of amethyst cathedrals and smaller broken pieces. 

I do like the colors in this large concretion with internal agate banding.

And away we go to explore the offerings.

I always enjoy seeing specimens collected from siliceous hot water deposits near Milford, Utah.

Anything you need from southeast Asia, except rocks and minerals.

Here is my favorite guy at the venue offering tasty snacks.

So this is Arizona and maybe rockhounds need to shoot claim jumpers.  Of course it is not uncommon to see, as Marty Robbins sang, "the big iron on his (her) hip."

Every rockhound needs genuine hide or fur to line their cases and drawers.

I always thought these were natural lingam stones but now realize they are linga (plural). I also believed they were collected by natives from a sacred river in India.  Somehow doubts creep in when I see thousands and thousands for sale in the US being pawned off as Hindu religious items guaranteed to increase your masculinity.

At last a shop selling rocks and minerals!

What appears as a crust of blue lavendulan (copper arsenate) is actually hundreds of tiny thin platy crystals; however, they measure in individuals less than 1 mm and are beyond the range of my scope.  The R points to one of a cluster of radiating individual crystals.  Total width FOV ~ 7 mm.

And, looking really hard at some stock I was able to locate a really nice piece of blue lavendulan.  The specimen appears as sort of a crust of intense electric blue on the matrix.  However, on closer examination under high power one can observe the crust is actually composed of very tiny aggregates of thin platy crystals, some of which form rosettes. An older label indicates collection at El Guanaco Mine, Santa Catalina, Antofagasta Province, Chile where MinDat noted 31 valid minerals and two type localities.  At the mine copper and gold veins are emplaced in Upper Cretaceous and Paleocene volcanic sequences.  I presume, but am uncertain, that both the copper and the arsenic could be the result of oxidation of the primary mineral, enargite [Cu₃AsS₄].

Lavendulan [NaCaCu₅(AsO₄)4Cl-5H₂O] is a hydrated copper arsenate and forms as a secondary mineral in “oxidized zones of some copper deposits” (MinDat).  So far, so good; however, I need to rely on the label for identification since a very similar mineral, lemanskiite, is known from the location (discovered in 1998).  In fact, the mine is the type locality for this copper arsenate.  Lemanskiite and lavendulan have exactly the same chemical formula but belong to different crystal systems-they are polymorphs.  Lavendulan is Monoclinic and lemanskiite is Tetragonal.  Trying to visually identify lavendulan from lemanskiite is above my pay grade!

As noted in other postings the arsenate radical (AsO4) is similar in size to the phosphate radical (PO4) and they often interchange.  Well, sampleite is a copper phosphate in a solid solution series with lavendulan.  If one substitutes lead for the calcite in lavendulan the mineral becomes zdenekite.  Learning is “fun”! 

So I am calling these tiny crystals lavendulan since I don’t carry around an XRD or something but knowing I well could be wrong!  These great- colored crystals have a vitreous to maybe a sub vitreous luster, are brittle, translucent, commonly cleave or fracture, and are quite soft (~2.5 Mohs).  Looking closely one can observe twins and the streak is a light blue.

I love life.  There’s so much to learn and see all of the time, and nothing nicer for me than to wake up, and the sky is blue.   Pattie Boyd

BLUE AFGAHNITE: TUCSON 2016

The 22^nd Street Show is one that I attend every year as it offers something for everyone!  The event is held inside of a giant tent (or so they say) anchored on a concrete floor.  Like most of the ancillary shows the parking lot is gravel and a tremendous amount of dust greets visitors upon arrival,  When I first attended the Show several years ago a hot dog was about the best one could do for lunch.  Today the food trucks have found the location and a variety of decent food is available.  The 22^nd Street location is also the building where many of “The Prospectors”  of TV “fame” hang out and sell their wares.  There seems to be a big market for signed posters and selfies with one of the celebrities!

Prospector Amanda at her booth.

How this stylized human figure composed of metal relates to rocks, minerals and fossils is beyond my realm of thinking. 

You name it; you take it home.

A wash basin for all with lots of partial cephalopods direct from Morocco.  I have often wondered how many cephalopods have been collected from Morocco??  

Item in abundance at 22^nd Street include a variety of fossils, especially large vertebrates.  Although illegal to collect from Federal lands in the U.S., the vertebrate fossils on display were collected, I presume, from private lands.

Last year I purchased several specimens of red spinel and ruby from a Pakistani dealer, and had some very nice conversations.  This year that particular dealer was absent, as was another dealer who always had several tables of minerals and crystals.  Instead the tent is increasingly being populated by some rather ecletic items of little interest to me.

However, I was able to hunt through some mineral tables and pick up a specimen of afganite, another one of those $5 minerals that displays a nice bright blue color and is rather uncommon in collections.  I felt fortunate in being able to ferret out this sample.

Fossil fish on a slab collected from the Eocene Green River Formation from near Kemmerer, Wyoming in the western part of the state.  If readers are ever in that area be certain to visit Fossil Butte National Monument.  The fish have been enhanced with a dark ink in order to provide a “better” display since these are objects de art rather than museum specimens.

A very nice reproduction of the Cretaceous carnivore Albertosaurus offered for sale by Tribold Paleontology over in Woodland Park, Colorado.  

An impressive reproduction of Torvosaurus, a large carnivore from the Jurassic Morrison Formation (Skull Creek Quarry, private) near Dinosaur, Colorado.

This is a lower jaw of a very young mastodon collected from the La Brea Tar Pits of California.  It must be an old specimen (20^th Century) since it is fairly impossible to get an actual specimen out of the preserve today.  Perhaps it came from a trade with some of the earlier paleontologists?

Skull of Basilosaurus, an Eocene whale from Morocco.  To early paleontologists it looked like a reptile hence the saurus moniker.  However, it actually in a mammal.  I did not check on the percent of reconstruction!

Afgahnite is a sodium, potassium, calcarous alumosilicate with a very complicated chemical formula: (Na,K)₂₂Ca₁₀(Si₂₄Al₂₄O₉₆)(SO₄)6Cl₆ .  It usually is a striking blue in color but at times the mineral is white, as is the streak.  Afghanite has a medium hardness of ~5.5-6.0 (Mohs) with a vitreous luster and a translucent to transparent diaphaneity.  It has a conchoidal fracture as occurs as massive blue material with scattered crystals (hexagonal system).  For example, the photos on MinDat are almost always nice doubly terminated dipyramidal crystals while my specimens only has the faintest outline of crystals. It is, or is related to, the feldspathoids, a group of minerals with a low silica content that are not found in rocks containing primary quartz.  My specimen has a matrix of metamorphic marble as do most of the specimens from the primary locality where the host rock is a skarn zone (where a limestone has neen intruded and cooked) in an Archean (Precambrian) gneiss and schist: Ladjuar Medam (Lajur Madan; Lapis-lazuli Mine; Lapis-lazuli deposit), Sar-e Sang (Sar Sang; Sary Sang), Koksha Valley (Kokscha Valley; Kokcha Valley), Khash & Kuran Wa Munjan Districts, Badakhshan Province (Badakshan Province; Badahsan Province), Afghanistan  Location from MinDat.

Photomicrograph of massive afghanite along with a cross section of a crystal noted by the arrow.  FOV ~1.6 cm.

Massive afghanite on matrix with arrow pointing to a crystal cross section shown in photomicrograph above.  FOV ~3.5 cm.