RUBY-IN-ZOISITE: ON THE WAY TO TUCSON

Sunset in camp.

I noted in the last posting that we were in the holiday time of the year and presented my Christmas “wish list.” We had zoomed past Halloween and the pumpkins and broom-riding characters. The orange pumpkins represent the bounty of the fall harvest and the orange fires lighting up the darkening night sky.  The Celts and Druids visited their spirit world ancestors around Halloween (All Hallows Eve) while many Christian religions celebrate All Souls Day and All Saints Day at about the same time.  Spirit worlds are dark and black as are “witches”, black cats, black bats and black spiders.  My favorite orange of Halloween is associated with candy corn!   

Before the masks were off the discount shelves we slipped into a purely American holiday, Thanksgiving. Here we celebrated the bounty of the harvest, especially yellow corn, perhaps the most staple grain during all episodes of U.S. history.  The orange pumpkins were still around although various “punkin chunken” contests certainly helped delete the supply.  Brown is often associated with the holiday since most fall and late winter leaves are sort of this drab color.

On or about December 22nd or 21st the Winter Solstice arrived in the Northern Hemisphere: the sun reached its most southern position directly above the Tropic of Capricorn, (~23.5 degree south), and the days were short and dark.

A few days after the Solstice, the traditional Christian-celebrated Christmas arrived on December 25^th.  The colors most associated with Christmas seem to be red and green (with white a distant 3^rd) although in the modern world blue, silver and gold are thrown into the mix.  Since Christmas in the northern hemisphere arrives during the often bleak, drab and gray winter, early European civilizations brought sprigs of greenery, for example pine boughs, into the house as a way to cheer up the inhabitants.  Even better would be a find of holly with red berries.  As a substitute for holly, early Christmas trees were decorated with red apples.  White represents the external world of snow.

Now, there also are a number of Christian religious reasons for the red, green and white used at Christmas; however, I will not delve into those issues.

Things just sort of chugged along with Christmas colors and an elf-like, dour Santa until 1930 when an illustrator by the name of Fred Mizen was hired by the Coca-Cola ® Company to create a happy Santa drinking a bottle of coke ®.  That first happy Santa was used as advertising in the December 1931 edition of the Saturday Evening Post.  The image was a big hit with the public so Coca Cola hired, in 1931, an illustrator by the name of Haddon Sundblom to create new Santa and Coke images on a yearly basis,  That relationship lasted for 35 years as Haddon created a jolly, plump and happy, older Santa Claus.  Haddon dressed his Santas in red and white to match the advertising colors of Coca Cola, his employer.  Red and White were also the colors of robes worn by Christian bishops.  Haddon evidently also borrowed from Clement Moore’s 1822 poem, A Visit from Saint Nicholas—you know, Twas the night before Christmas and all through the house… chubby and plump, a right jolly old elf.

So today, a non-religious Christmas celebration is usually represented by a green tree (pine, spruce, fir) and a red and white Santa.  Sundblom’s Santas radiated warmth from a grandfather like person, one who loved children and so snacks were left behind by the nice kids.  Almost any person of my age living in North America would recognize Haddon Sundblom’s rendition of Christmas Santas.  Coca Colas advertising was a stroke of genius and as a boy I always looked forward to seeing the newest editions and would ask my father to please bring home a coke along with an advertising poster.

So, what does all this banter mean when it comes to minerals?  Probably nothing but as the days got shorter and darker I sometimes lounged around thinking how to relate minerals to some sort of a story.  After 328 postings I sometimes lose my concentration, but not on this one---what would make good Christmas minerals, related red and green combinations?  So, I started putting this little offering together but was waylaid by a number or other opportunities---like spending time with my family in a condo at the Colorado ski slopes.  Now, I don’t downhill (love x-country) but sitting by a fireplace with a good book is a great way to spend an afternoon/week and so it was, and the beginning of 2019 arrived and disappeared.  By then it was time to begin packing my 5^TH Wheel for a visit to the Tucson Gem and Mineral Show making certain to arrive in mid-January for a camp near the Superstition Mountains in Lost Dutchman State Park.  So, here I am still thinking I need to get this post out!

In my way of thinking, the perfect Christmas “mineral” would not be a single mineral but a semi-precious gem called ruby zoisite, ruby-in-zoisite, or anyolite.  Specimens are composed mostly of the green mineral zoisite (chrome variety) accompanied by opaque dark red ruby crystals and often by black crystals of the amphibole pargasite (formerly identified as the hornblende amphibole tschermakite).  Anyolite specimens are commonly used to make cabochons, beads, tumbled stones and sculpted objects (elephants seem to be a favorite). But any way you look at it, the red ruby presents a great contrast to the green zoisite—the perfect Christmas stone!

Zoisite is a calcium aluminum silicate [Ca₂Al₃(Si₂O₇)(SiO₄)O(OH)] that would probably be unfamiliar to most people except for a single gemmy variety.  Most zoisite seems nondescript and occurs in a wide variety of shapes from massive to prismatic crystals.  The elongated crystals that belong to the Orthorhombic Crystal System are perhaps the most common and they are striated along the C-axis (the long axis).  Zoisite crystals also commonly radiate out from a center with the entire mass forming a “circle” (two-dimensional view).  Crystals occur in a variety of colors from red and pink to green and blue to brown or gray---take your choice.  In anyolite the tiny zoisite crystal have a green tint imparted by trace amounts of chromium. Zoisite is fairly soft (as a gemstone) and is usually stated as 6.0-6.5 (Mohs).  It is brittle, transparent to translucent to opaque, and can have a vitreous to pearly luster. It is found in a wide variety of environments ranging from contact metamorphic rocks to regional metamorphic schists to granite pegmatites.  It seems to be one of those minerals that is tough to pin down.

This beautiful emerald-cut tanzanite ring is offered for sale by Diamondere Inc. The total caret weight is 4.97 and the price is $8277.  Photo courtesy of www.diamondere.com.

As I stated above, who would recognize zoisite except for the sought after gemmy variety tanzanite!  Discovered in the late 1960s in Tanzania, tanzanite can be a beautiful blue color and is a giant hit on the gem market ranking only below sapphire as the most popular blue gemstone. The blue color in tanzanite is produced by trace amounts of vanadium; however, the natural deep blue gems are scarce and today most gems are produced by heating brown or green tanzanite to a temperature of ~600 degrees C when the oxidation state of the vanadium changes and the blue color is emphasized.  Tanzanite gems are graded similar to diamonds—clarity, color, size, and cut.  The cleaner (no inclusions) and bluer the stone the higher the value.  Good cuts require numerous facets to bring out the brilliance.  These good stones bring prices of thousands of dollars per caret.  For a great series of articles on the grading of tanzanite gems check out the series of articles by Lapigems at       http://www.lapigems.com/Articles/Tanzanite-Color-How-it-Affects-Value.aspx.

Tanzanite is one of the most popular gemstones on the market but is rare as all stones are mined from about 8 square miles in an area around Mt. Kilimanjaro in Tanzania. It might have remained a minor gem after discovery if Tiffany and Company had not put on an advertising blitz to get the public interested in this great new gem!  The blitz worked and today the company TanzaniteOne mining Ltd. Is the major player and seems to have a huge influence of the price (as does the government of Tanzania, and natural disasters such as floods).

So, if zoisite, other than tanzanite, is relatively unknown then ruby, the other main constituent in anyolite, is one of the best know gems.  In fact, ruby may be the most popular, and the most expensive, of the colored gemstones (others argue for gem emerald, a green beryl). A clear, large, pigeon-blood red, and well-cut ruby can bring thousands of dollars on the gem market.  Unfortunately, the ruby in anyolite is fractured and nearly opaque and therefore of non-gem quality.  However, it still contrasts nicely with the green zoisite and is very showy in cabochons.

Ruby, an aluminum oxide, is actually a variety of the mineral corundum (Al₂O₃) where minor amounts of chromium provide the red color.  A second variety of corundum is the multi-colored gem, sapphire, colored by minor amounts of titanium and iron. The most valuable sapphires are corn flower blue in color; however, several other colors of sapphires appear on the market.  Any colored corundum that is not red is a sapphire.

Corundum is a name that is well known to beginning geology students as it occupies #9 on the Mohs Scale of Hardness—sandwiched between #10 diamond (the hardest) and #8 topaz.  Corundum can be found in both metamorphic and igneous rocks that are silica-poor but rich in aluminum. However, the mineral is so hard that many of the gemstones are panned from alluvial gravels as the remains of eroded parent rocks.  Crystals are often six-sided, tapering, hexagonal dipyramids.  Both gem sapphires and gem rubies generally come from southeast Asia.

The third component of anyolite is the amphibole pargasite, a sodium calcium aluminum magnesium silicate.  Actually, pargasite is a group name with several modifiers to indicate a dominant element.  I presume that the anyolite black (actually very dark green) pargasite indicates the presence of iron.  In a previous post (2/16/15), the pargasite I described from Pakistan was a a nice green color, perhaps with minor amounts of chromium?

I purchased my specimen of anyolite a couple of years ago at the fall Denver Show.  It was collected from the major anyolite locality in Tanzania, the Mundarara Mine.  MinDat also reports a minor collecting locality near Drosendorf-Zissersdorf, Austria.  As best I can determine, anyolite is the product of metamorphic activity.

Anyolite or ruby-in-zoisite.  The zoisite, (Z) is composed of tiny prismatic crystals.  Pargasite (P) crystals are larger (up to 3 mm) while the ruby (R) is badly fractured.  Width of photo ~10 cm.

So, there it is—the perfect Christmas rock.  But now it is 77 degrees here in the desert, the sun is shining, a jolly old Santa seems ages ago and the length of daylight has increased 21 minutes since the Solstice.     The Tucson shows are just two weeks away –happy days are here again!