Wednesday, February 14, 2018

KYANITE: TUCSON 2018 JOGS


After hitting the Westward Look Resort Show I headed over to the JOGS Tucson Gem and Mineral Show.  JOGS is one of the “giant” shows with several hundred dealers (I was too lazy to count) and is restricted to wholesale buyers and “buyer tags” are required for entrance.  I was able to attend with a qualified buyer and purchase a “public guest” ticket.  JOGS is hard to describe—gigantic, more jewelry than I have ever seen in one place, beautiful multi-thousand dollars rings and pendants, faceted gem stones of all kinds from locations around the world, less expensive sterling silver jewelry with nice semi-precious stones, lots of findings (parts for jewelry making), and a few minerals (mostly amethyst cathedrals).  I also noted that many/most dealers had a minimum purchase, usually $200-300.  This certainly was a venue for purchasing jewelry in large lots at wholesale prices for later retail sales.  I listened as one buyer purchased 300 black onyx rings of mixed sizes, mostly 6,7,8.  Each ring was packed in an individual “cellophane” bag with a size label. But I must admit that after looking at a couple of hundred booths most items appeared similar!
Large clusters of elongated kyanite crystals priced at ~$100---$150. The largest single crystal is ~20 cm.
The most impressive mineral display, IMHO, were the large kyanite specimens from Minas Gerais, Brazil (the best information I could get from the Dealer). Kyanite is an aluminum silicate [Al2(SiO4)O] that comes in a variety of colors (white, black, blue-gray, gray, orange, green, black, and more) with vivid blue being the common variety and the favorite of collectors.  Crystals, often bladed and long, are transparent to translucent with a vitreous to pearly luster.  It is a very distinctive mineral and seems easy to identify.  In addition to form, kyanite has a variable hardness--- around 5 (Mohs) parallel to the C-Axis (long part of the crystal) and around 7 (Mohs) perpendicular to the C-Axis.
My hand specimen of kyanite ~14 cm. purchased for $5.  The light colored matrix appears to be talc and a small amount of quartz.
Kyanite is a metamorphic mineral and its presence indicates a specific temperature and pressure range.  It is one of three aluminum silicate trimorphs with the other two being sillimanite and andalusite.  I have other colors of kyanite in my collection (not with me) and several specimens of the other trimorphs; therefore, since I have a manuscript partially completed I will not offer additional information on kyanite.  I just need to get a photo or two out for the readers.     

Monday, February 5, 2018

TUCSON WESTWARD LOOK RESORT: FANTASTIC MINERALS


Each year the beautiful Westward Look Resort in the foothills west of the Catalina Mountains hosts a short (4 days) but fantastic show.  I believe there are 40 dealers at the venue and all bring some of their most spectacular specimens (along with their spectacular prices—at least to an ole mineral bum like me).  But, the exhibits in each room are open and free to the public for viewing (and buying).  Most visitors attend the show since viewing the room showcases are like walking into a fine mineral museum.  And, the dealers are more than happy (if their time permits) to have friendly conversations and answer questions.
The photographs below are certainly not professional and shot through the showcase glass.  But, perhaps the readers can get some sense of these nifty minerals. 

The mineral rooms at the Westward Look.

Azurite from Mexico.

A mixture of smaller specimens.

Sulfur crystals from Italy by Coloradoan Dave Bunk.
 
Two amazonite and smoky quartz assemblages collected from the Icon Pocket by Joe Dorris of Colorado Springs (Pinnacle 5 Minerals).  However, only the lower specimen was for sale by Joe.  The upper was in an adjacent room.

Tough to get the correct green color on these emerald crystals (a variety of emerald).  ~3.5 inches high.  Rumor has it the price was $200k but the crystals were clear and gorgeous.
Fantastic smaller specimens.
Brucite, a magnesium hydroxide mineral.
The beautiful aquamarine, a variety of beryl.

Sunday, February 4, 2018

TUCSON SHOWS AT LAST: TOURMALINE



 
Well, it has finally arrived, or at least I have arrived in Tucson to bum around at the Tucson Gem, Mineral and Fossil Shows.  At my best count there are ~60+ different venues/shows this year anchored by the Tucson Gem and Mineral Show® (TGMS) scheduled for the Tucson Convention Center February 8-11.  Most of the other venues/shows run during the two weeks preceding the end of the TGMS—in other words about the first two weeks of February, give or take a few days on either end.  My goal this year is to visit 15 or so of these ancillary shows.  Some of these other venues are huge; for example, the G&LW Tucson Show/Holidome has over 500 booths (as best as I count count) while other small shows have a half-dozen booths.  Some shows are in hotels and utilize individual rooms while others, such as the large 22nd Street Show, erect giant, and I mean really large, tents.  Other more “mom and pop” shows have dealers selling from trailers or individual sun/rain protectors or pickup beds open to the elements.  There are several venues that specialize in specific areas---perhaps beads, fossils, high-end minerals; however, most are a mixture of “everything” from clothes to rugs to dinosaur mounts to all sort of minerals and rocks.  In addition, specific shows such as the large JOGS Tucson Gem and Mineral Show are restricted to wholesale buyers and “buyer tags” are required for entrance. All in all, the shows/venues represent an amazing experience.

One of the first shows I headed for was the 22nd Street Mineral Fossil and Gem Show, a cornucopia of pleasures.  My major purchase was a grouping of Brazilian tourmaline crystals.  No, the crystals were not gemmy but I liked the piece for display and it was in my monetary range (cheap) of $5. 
One of the "big" tents at the 22nd Street Show.

I have always enjoyed the brecciated jasper termed mookite collected in Australia.

Almost all shows have Eocene fish collected from the Green River Formation near Kemmerer, Wyoming.


How about a sting ray from the Green River quarries.
There are always displays of magic minerals.  In a couple of weeks I am taking a piece of amethyst and heading to a vortex near Sedona.

You can always find a variety of merchandise at the 22nd Street Show.
Tourmaline is now classified as the Tourmaline Group with several end-member species created by common solid solution series.  Virtually every member of the Group seems in solid solution with other members.  Every few years a new classification pops up.  For example, on 1 February 2018, I noticed an abstract by Bosi stated that his new study “has direct implications for the tourmaline nomenclature, as well as on petrogenetic and provenance information. Some assumptions behind the classification scheme of tourmaline have been reformulated, revealing major agreement and significant improvements compared to earlier proposed scheme.”  So, if you want the newest scoop locate his paper in the American Mineralogist. Otherwise I will offer some generalities.

Tourmalines (refers to the Group) are boron silicate minerals with a large variety or combination of calcium, potassium, sodium, aluminum, iron, lithium, vanadium, magnesium, manganese, chromium cations (the positive charged elements) thrown in. For example, the well known variety elbaite is: Na(Al1.5Li1.5)Al6(Si6O18)(BO3)3(OH)3OH. The chemical formula is really hard to understand but I will toss out the general formula from www.mindat.org:


                  A(D3)G6(T6O18)(BO3)3X3Z

A = Ca, Na, K, or is vacant (large cations);
D = Al, Fe2+, Fe3+, Li, Mg2+, Mn2+ (intermediate to small cations - in valence balancing combinations when the A site is vacant);
G = Al, Cr3+, Fe3+, V3+ (small cations);
T = Si (and sometimes minor Al, B3+);
X = O and/or OH;
Z = F, O and/or OH.
 
As you can guess there is much cation substitution, so the group has many different varieties; MinDat lists 39 different “kinds” of tourmaline.  A couple of members that many of us recognize would include the common black schorl (iron rich form and the most common variety in rocks) and the pink elbaite. Bosi (2018) noted that “tourmalines form the most important boron rock-forming minerals on Earth.”
Pink elbaite crystals in a off white matrix that is some sort of a feldspar mineral (maybe microcline, maybe not). Width of photo ~8 cm.
Elbaite, a sodium lithium aluminum boron silicate (in the formula above sodium would occupy Position A of large cations while lithium and aluminum occupy Position D of smaller cations). It is probably the most colorful of any of the Group members and in some case even bi-or tri-colored (for example the popular watermelon tourmaline with zoned crystals displaying a green outer layer over a pink center).  The best known colored elbaite is probably the pink variety (sometimes termed rubellite), and that is what I purchased. Elbaite belongs to the Hexagonal Mineral System and often is found as elongated prismatic, striated crystals without cleavage.  They also have a very distinguishing rounded triangular cross section.  Gemmy varieties are vitreous and transparent while less gemmy crystals are more translucent.  Tourmaline is about the hardness of quartz at 7.0-7.5 (Mohs) and gemmy crystals of many colors are in high demand for faceting, carving and cabochons. 

The seller stated that the specimen was from one of the mines in the State of Minas Gerais, Brazil-----an area of hundreds or thousands of mines.  MinDat states that “probably the best known of these are the pegmatite minerals like tourmaline, beryl, quartz etc. that come from the pegmatites in the north west granitic region of the state and whose center, business wise if not geologically is the town of Governador Valadares.”  So, I will settle for that general area!

The pink color of elbaite is probably due to the high lithium content; however, this variety also occurs in about every color of the rainbow and I am uncertain about other color chromophores.   In fact, I have heard of elbaite referred to as lithium tourmaline.  I also understand that the lithium (and the boron) is very important in lowering the magma solidification temperature.  
  
So, the Tourmaline Group is a very complex assemblage of minerals and understanding much of the mineral chemistry is above my pay grade.  However, the various tourmalines often make spectacular gemstones and display specimens.  I was impressed in observing a very large “pile” of these masses of crystals at the venue.

REFERENCES CITED

Bosi, F.,2018, Tourmaline crystal chemistry: American Mineralogist, v. 103.