TUCSON: CLINOCHLORE v. KIMMERERITE AND TUCSON CITY CENTER

Another very large venue at Tucson is the Arizona Mineral & Fossil Show held at the Hotel Tucson City Center.  This is a fairly recent name and many of us still refer to it as the Inn Show.  Whatever the name, this Show produces a wide variety of dealers: two levels of the hotel (a “hollow square arrangement”) on both the inside and the outside are filled with “room dealers;” ballrooms of the hotel have dealers (mostly finer mineral specimens and jewelry); tents are arranged in spaces near the front and one side of the hotel; and dealers are positioned in the lobby.  In addition, the courtyard has a swimming pool, a few tents, and dinosaurs (well at least replicas). A large tent at the external side held Fine Minerals International, while Pinnacle 5 Minerals from Colorado Springs had a room of fine amazonite crystals. Several international dealers specialized in minerals from their home countries, while other rooms held more “mom and pop” specimens.  Fossils were abundant, and the hotel bar seemed busy during both of my visits. During the weekend the venue was filled with happy children getting a photo op at the dinosaurs.  I did not get a photo but the most impressive piece, in my opinion, was a 100 carat, very gemmy, faceted pink kunzite set in a gold ring—well out of my price range but enjoyable to ogle.

The following represent a few of my favorites:

This is a very nice marine reptile termed ichthyosaur or "fish lizard."  Many persons confuse icthyosaurs with dolphins; however, their similarity represents a great case of convergent evolution--evolution of similar features in species of different lineages.  Ichthyosaurs are reptiles while dolphins are mammals.

 

Dealers mining the Eocene Green River Formation of western Wyoming always contribute really nice specimens. Among them: a complete palm leaf (upper), a 63 inch palm flower (middle), and a lower 8 foot crocodile (Borealosuchus wilsoni).  The flower had a price of $60,000 while the crocodilian could be taken home for $550,000 (I ordered 2!).

A pretty ferocious looking raptor does not seem to scare the resting child in the background.

I guess this half mount represents a T Rex; however, the cast maker must have copied from an old book as they created a "tail dragger." 

Now here is the "real thing"--a well preserved skull of a horned dinosaur (encased in white plaster).  Unfortunately, the skull is flattened and is not available for mounting.

I thought this docile looking herbivore seemed at home in the palm trees.

I always enjoy the large display of Canadian (Alberta) ammolite, a name give to iridescent covering on large Cretaceous ammonites. Small amounts of ammolite are found in South Dakota and Montana but almost all jewelry or display specimens come from Alberta.  Rockhounds should realize that the Province has strict collecting rules--see Blog posting November 22, 2015.

I love this learning display as it shows fake amethyst points "made in China".

This was advertised as the "world's largest kunzite crystal at near 30 kilos."  The dealer said it was collected from Brazil but could not give additional information.  Kunzite is the pink variety of spodumene (lithium aluminum silicate).

I have posted the photo before; however, it is such a great display.  How often do I look at slabs of Moroccan trilobites wondering if they are "real."  Notice the great external features and then look at the cut slab--no internal features.  Some great carving and painting though. 

This is an interesting top view of a petrified wood "trunk" due to its blue color rather than the "normal" orange/red color.  There was no locality info but I am guessing Indonesia.

This was one of my favorite specimens--a polished quartz crystal included with tourmaline inclusions.

Take a peek at the sign--Nature's rarest and most extreme minerals.  But, the tent was filled with amethyst crystals in the cathedrals. Not all that rare!

I did manage to snag a mineral or two at the mineral dealers including one that is sort of "different."  I have reported on the mineral clinochlore in a previous post and described it as some crud on the quartz (see Blog posting March 22, 2016).  Clinochlore is a member of the chlorite group of minerals, a common group of ubiquitous minerals occurring in a wide range of temperature conditions in metamorphic rocks, igneous rocks, and hydrothermal rocks.  We think of chlorite minerals as being green in color; in fact, chlorite essentially refers to a green color in objects other than minerals (some chewing gum). However, the chlorite minerals are phyllosilicates that have a wide variety of cations (positive charge that impart the color) to go along with the silicate anions (negative charge).  Phyllosilicates are also "sheet silicates" that form parallel sheets of the silicate tetrahedra and the minerals themselves reflect these parallel sheets--think biotite, muscovite, talc, kaolinite clay, etc. 

"Common" clinochlore is a magnesium aluminum silicate [Mg₅Al(AlSi₃O₁₀(OH)₈] and usually appears as stacks of sheets that are soft, greasy in luster, and some sort of green in color.  Clinochlore often contains iron and as iron increases the mineral becomes chamosite in a solid solution series. But an interesting variety of clinochlore is kammererite, a [purple to pink to red, chromium-bearing variety officially known as chromium clinochlore Mg₅(Al,Cr)₂Si₃O₁₀(OH)₈].  It is not a common mineral (might be rare) and the best specimens may be from the Kop Krom Mine, Kop Daglan, Erzurum Province, Anatolia Region, Turkey.  That mine closed in 1991 and specimens from other localities are not as good as those from Kop Krom.  My specimen has an older looking label and at any rate would have been collected before 1991.

A closer view of the smaller crystal seen below.  It is a more "iridescent" and more gemmy than the larger crystal below.  Notice the cleavage planes on the asymmetrical hexagonal crystal.  Width of "bottom" of triangle ~1 mm.

 

Two views of a nice large, asymmetrical pseudoheaxagonal crystal of kammererite showing the sheet like structure.  More gemmy but smaller crystals are scattered.  The matrix is composed of smaller masses of sheets.  Width of "bottom" of triangle ~3 mm.

A group of nice kammererite crystals.  Most good crystals are asymmetrical pseudohexagonal. Matrix is composed of small micaceous crystals.  Width of photomicrograph ~1.5 cm.

A very nice gemmy crystals in a matrix of small sheet-like kammererite plates.  The mineral in the upper left are sheets of "normal" clinochlore. Width of photomicrograph ~1.5 cm.

Kammererite is soft at ~2.0--2.5 (Mohs), transparent to translucent, has a greasy feel, and leaves a white streak.  Since it is a sheet mineral, specimens have that perfect "mica-like" cleavage but stacking of the sheets often produces pseudo hexagonal "crystals." It belongs to the Monoclinic Crystal System.  As for the geology at the collecting locality, the best I could locate is that the Kop Krom was a former chromite mine.

Clinochlore, including kammererite, is the result of metamorphic and hydrothermal alteration of iron- and magnesium-rich silicates such as amphiboles and pyroxenes, and especially of oceanic basalts. The kammererite variety seems to be the result of weathering of chromium-rich serpentine.  Weathering of clinochlore produces the silicate mineral vermiculite and several clay minerals belonging to the Smectite Group.  In fact, some authors classify Chlorite Group minerals as “clay minerals”.

So, it was another good day.  In fact, I returned a second time to explore rooms on the second floor that I missed on my initial visit.