Sunday, February 12, 2012

So Where Did That Amethyst Geode Come From?

Mother Nature’s Part – Almost all amethyst geodes began life when a volcano erupted.  As the lava flowed to the surface, gas pockets were entombed in the solidified lava, usually in a form of volcanic rock called basalt.   Deep below the solidified basalt, Mother Nature continued to maintain a very hot molten lava structure.  From time to time, super-hot fluids would rise from the molten lava area and find their way to the gas pockets through small cracks and crevices in the basalt.  These liquids carried with them the mineral components to build a beautiful crystal.  In the case of amethyst, these involved the components of silicon dioxide (SO2, the chemical formula for quartz) and small amounts of iron ions.  As the quartz crystalized, small impurities of the iron ions would take the place of silicon in some of the molecules, providing the basis for amethyst coloring.  If the molecules were then also subjected to relatively high heat levels and small amounts of radiation, a beautiful purple amethyst crystal would be born.  Heat most often would come from the adjacent lava structure, and the tiny amounts of radiation required would often come from rocks like granite or phosphorus that give up small amounts of radiation as they slowly decay.

Over millions of years, Mother Nature would typically do many cycles of this super-hot, mineral carrying liquids inundation process.  Depending on the exact mineral composition of the liquids at various times, many colors of crystals and indeed different mineral crystals could be formed.  Very often, the quartz that forms in a geode could include large amounts of clear or milky white quartz in addition to the purple amethyst. Less often, entirely different kinds of crystals can be formed on top or embedded in the quartz……most often this takes the form of very interesting, accenting crystals of calcite.  Usually the calcite crystals are clear or white, but occasionally they are a very attractive hue of pink.

Where on Earth Are the Geodes Found? – In principle, geodes can be found anywhere on earth where volcanos helped shape the earth’s crust.  Volcanos are important mountain range builders, and most existing sources of geodes are in or near mountains.  For amethyst, some of the most important deposits are found in South America.  A huge area in southern Brazil contains large basalt structures, many of which contain geodes of varying qualities.  Brazil is by far the largest exporter of amethyst geodes by volume.  Across the border in Uruguay, a much smaller area contains important deposits of some of the world’s very best colored amethyst geodes.  Also nearby, in eastern Bolivia, there are a few mines that contain amethyst deposits that include cavities with enormous crystals.  It is impractical to extract these large crystals in complete geodes owing to the massive quantities of rock involved, but from time to time clusters or individual crystals extracted from those structures make their way to the USA.

What Other Crystals Form in Solidified Lava? – Many kinds of crystals form in the pockets and crevices that gas pockets created in solidified lava.  In the rock type basalt, several kinds of zeolite minerals also form lovely geodes.  Amongst these are brilliant green or crystal clear apophyllite, often accompanied by peach colored stilbite or white scolecite which are found in large quantities in the Decca Flats area in India.  Also commonly forming in basalt structures are other forms of quartz like agate, chalcedony, onyx and jasper.  In granite pegmatites (granitic lava that solidified underground, often in a columnar structure) many of the world’s finest gemstones crystalize.  These include diamonds, emeralds, topaz, tourmalines, and exquisite individual quartz crystals.  These granitic structures are also found in areas shaped by volcanos.

What About Citrine Cathedrals? – Citrine is a relatively rare, naturally occurring version of quartz that has a yellow or yellowish brown coloring.  These are most often found in moderately large single crystals.  However, there are also geode/cathedral forms of citrine that were created when Brazilian miners exposed medium grade amethyst geodes to high heat…which permanently and attractively changes the color to yellow to yellowish orange.  The resulting citrine cathedrals make very attractive décor additions, where their unique color is of interest.  All such citrine cathedrals are the result of this high heat treatment process, so if someone offers you a “natural citrine cathedral” you should be skeptical.

So How Did Man Extract the Geodes? – Extracting geodes is basically a well refined mining process.  Although the process involves heavy equipment and explosives to reach geode producing areas in the basalt, all of the main work involves a hefty dose of manual labor.  The geodes are first exposed through mining efforts.  The basalt is removed revealing the shape of a geode in the floor, wall or ceiling of the mine.  The next step is to examine the interior of the geode to determine if the crystals are of high enough value to pay for the manual effort required to extract the geode.  This is most often done by cutting an inconspicuous hole in the geode and inserting a small light and viewing device that resembles a flexible periscope. 

If the crystal is an ordinary color like milky white quartz, the geode will be bypassed and often destroyed in subsequent mining efforts.  If the crystal is amethyst of a good color, then the geode will be manually chipped out of the basalt a little at a time.  This process can take days of labor for a single geode.  Once the geode has been removed from the base basalt, it is then carried to a workshop some distance from the mine.  This typically involves using a wheel barrow to manually remove it from the mine itself, and then a wagon, narrow gauge rail car, or truck to carry the piece to the workshop.

At the workshop any remaining basalt is removed and the geode is cut open to display the crystals.  Often geodes are of a broadly columnar shape.  These will be cut vertically along the longest portion of the geode.  These pieces are then prepared as a form known as a cathedral.  The geode at this early stage has an exterior surface that contains many, many sharp protrusions of the base level of the quartz.  These are dangerous to both the workers and to the ultimate customer.  To avoid the attendant danger of cuts, the geode is coated in a thin layer of cement to cover the sharp points.  The cement is then ordinarily painted with a flat black color to enhance the aesthetics of the purple amethyst crystals.  If the piece is to be displayed as a cathedral there will often also be a small fill of cement at the bottom of the piece to form a level structure on which to stand the piece.  Any remaining sharp quartz points along the entrance to the geode are then polished to a smooth surface for both appearance and safety reasons.

Sometimes, the crystals will be of such high quality the geodes will be displayed on steel stands.  This is often the case with geodes from Uruguay, which is world renowned for the extraordinarily rich deep color of its amethyst.

How Do the Geodes Get to Me? – Geodes are heavy.  A single cathedral that stands 40 inches or so tall, will typically weigh over a hundred pounds.  They are also vulnerable to breakage.  Remember the geode is a relatively thin exterior of quartz with a large empty space inside.  This structure makes the geode vulnerable to breaking, especially when exposed to the shipping process…... which sometimes feels like it attracts all of the world’s 800 pound gorillas.

To protect the geodes, they are individually packed inside of wooden crates….both for shipment to touchstone and for shipment to a customer’s location after they choose a geode they like.  Crating costs are relatively inexpensive in Brazil where hundreds are made for a single shipment to the USA.  These crates are built for a single use and shipped strapped together to combine the strength of all of the crates.  In the USA, crating costs of $200-300 for a 40 inch geode….. made to order for a single geode in one of our locations is quite common.  This does not include the cost of shipping the piece, which varies a lot based on distance and the delivery type on the receiving end……where residential costs more than commercial, and “white glove delivery” inside of the home or office costs more than curbside delivery in your driveway.

How Are Amethyst Geodes Graded? – Brazilian amethyst in particular goes through a grading process.  The Brazilian system uses a 1-14 grading system that values:
          1.)    A very thin or complete absence of ordinarily colored quartz as the base of the crystals.
          2.)    Deep rich purple coloring
          3.)    Large, perfectly shaped individual crystals.
          4.)    Uniform color from the tip to the base of individual crystals.

How Does touchstone gallery Choose the Geodes it Markets? – touchstone sees its role as supplying very attractive geodes that are suitable for use as exquisite accents in your home or office décor.  As a result, we choose only very high quality geodes to market.  We are always marketing Brazilian geodes of grades 10 -12 which have great color and very little ordinary colored quartz in their bases,……. and when we can get them, we include a few of the quite rare grade 14 geodes in the mix.  These geodes are great choices if you want to add a dramatic piece to your décor.

touchstone also provides very high quality Uruguayan geodes when they can be sourced.  These are often displayed on polished steel stands.  Uruguayan amethyst has some of the best color of any amethyst found on earth.

We also mostly limit ourselves to what we call “two man rocks”.  Only rarely do we choose pieces that two men cannot lift as a team.

We invite you to view our current offerings in our galleries in Santa Fe, Scottsdale, Sedona and Taos, or online at www.touchstonegalleries.com. If you are looking for something you do not see at one of our galleries or on our website AND you have the time to wait for a sourcing process that can take months, let one of our gallery team members know and they will help begin the search process.

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