Mineral of the Month--May
By Karissa Hendershot
Welcome to another guest author's article! This month,
we are visiting Tsavorite, a newly
popular gemstone. Enjoy!
In this month's installment, we will pay a brief visit to a bright
green favorite: Tsavorite.
A gemmy garnet by nature, when faceted, this stone is adorning modern jewelry the world
Our guest author, Karissa Hendershot, is DMS's current President. Although her first
is for fossils, her knowledge of and experience with minerals has grown over the years.
join us for a long-awaited look into garnets.
||This exceptional 7.24 ct. Tsavorite cushion
was mined from the Bridges' Scorpion mine and is now on loan to The Smithsonian Museum in
Campbell and Judith Bridges, Tsavorite USA, Inc.
CHARACTERISTICS OF TSAVORITES
Tsavorites are not an acknowledged mineral
species. Instead Tsavorite is a variety of Grossular garnet.
trade name for green grossular garnet, was named by Tiffany & Co after the location,
where it was first discovered by the Geologist Campbell Bridges in 1968.
Photo by ICA Gem Bureau
Specific Gravity 3.603.68
Refractive Index 1.740; Singly refractive
Crystal System Cubic
Light to Deep Green
Enhancements Generally None
Ultrasonic: generally safe, but risky if the gem contains liquid inclusions. Steamers: not
safe. The best way to care for Tsavorite garnet is to clean it with warm, soapy water.
Avoid exposing it to heat or acids.
Sources. The original locality for Tsavorite was Kenyas Tsavo
National Park, but today important deposits of gem tsavorite have also been found in
Tanzanias Lindi Province.
Why is it called Tzavorite or Tzavolith respectively if it is after all a
green Grossularite from the colorful Garnet family? Naming
gemstones is performed according to certain rules. Modern mineralogical nomenclature
demands that gemstones are given a name ending in "ite". To honour the Tzavo
National Game Park and the Tzavo river running through this area, Henry Platt , the former
president of Tiffany & Co, who accompanied the gemstones rise to popularity, had
suggested the name Tzavorite. Sometimes, however, Tzavolith is used but both denote the
same stone. The ending "lith is simply the Greek word for "stone.
Additionally, the z is often replaced with an s changing the
spelling from Tzavorite to Tsavorite. Both version seem to be perfectly acceptable
spellings for the gem stone as well as the area the garnet was named after.
knows about precious diamonds, rubies or emeralds. But only the real experts know about
tsavorite. Tsavorite is also called green grossular garnet. It is a rare gemstone mined in
the Kenyan part of the Mozambique belt which is in the bushland along the frontier between
Kenya and Tanzania in the Tzavo National park. The sparse mines there are situated
in a uniquely beautiful landscape of dry grassland with bare and dry hills. It is a
dangerous region, where snakes feel at home and now and then a lion will hunt for prey.
green Tsavorite is rather a young gemstone with a truly ancient geological history.
In 1967, the British geologist Campbell R. Brides was prospecting for gemstones in the
north-eastern part of Tanzania. Suddenly he came across some very odd, potato-shaped stone
objects. And like in a fairy tale, he found breathtakingly beautiful green grains and
crystal pieces inside these weird objects. Gemological tests showed that he had discovered
green grossularite, a mineral which had up to then been considered very rare, which
belongs to the colorful Garnet family. The stones were very beautiful and of high
transparency, so that his find made experts sit up ad take notice. Even Tiffany & Co.
in New York expressed their interest in the newly discovered green jewel. But in spite of
all efforts it was impossible in those days to get an export license for taking these
stones out of Tanzania. Campbell Bridges, however, did not admit defeat. As geologist he
knew that those layers in the soil which carry gemstones are generally not limited to just
one spot, but usually stretch out over vast areas and such a layer was what he had
encountered according to his opinion. After all, the stone belt which accommodates most of
East Africas gemstone mines is truly ancient.
Bridges stubbornly continued his search. His theory that the gemstone loaded vein might
even extend into the Kenyan territory finally set him on the right track. In the year 1971
he discovered the brilliantly green gemstone for a second time, this time in Kenya, where
he could officially register his find and could start exploiting the occurrence. This was
the beginning of a new adventure: in order to protect himself from wild animals Bridges
lived in a tree house at first. And as he did not want his treasure to be stolen, he
cunningly employed the workers fear of snakes and had the rough stones guarded by a
python snake. It was a beautiful find indeed. Unfortunately, however, the stone was only
known to experts. This changed quickly when in 1974 Tiffanys started a special
promotion campaign making Tzavorite well-known in all the USA in only a short time. Other
promotion campaigns in other countries followed, and soon Tzavorite was a name known
covered by the ocean millions of years ago at a time when the continents where moving
around a great deal more than they are now. Layers of organic sediment were
deposited, and compacted to form shale. The land was subjected to intense heat, pressure,
folding and uplift, metamorphically changing the ocean floor into new minerals. This
twisting and torturing of the rocks gave birth to the unusual gemstones of East Africa,
many colored by the vanadium which is plentiful in these rocks.
Most deposits of
tsavorite are found in small and unpredictable pockets. From a mining standpoint, it
is very difficult to figure where to mine next. There have been about 40-50 different
areas where tsavorite has been mined. Today, only four mining ventures are still
producing. The Scorpion Mine owned by Campbell Bridges is located in Mindi-Kandashi,
southeast Kenya. The Aqua Mines, with 3000 acres are located in the Tsavo National Park
near Kasigau, Lualenyi Mine is located in Voi, Kenya and a new tsavorite-producing
area was recently discovered in Lokirima, about a thousand kilometers northwest of the
previously known localities. Hopes are high that this location will start producing rough
suitable for faceting.
often found in pods which miners call potatoes. The green color is most often due to
vanadium or chromium. The early geology which formed tsavorite shattered most of the
crystals. Tsavorite mining requires expensive earth removal equipment. It is very rare to
find tsavorite in sizes larger than three carats. Most tsavorites are carat size or
smaller. (Ed. note: The largest tsavorite we have ever bought/sold was a gem 15.41).
Compare this to the wide availability of tanzanite above 10 carats.
Tsavorite has a
vivid green color with a high refractive index and double the dispersion of emeralds,
giving tsavorite potential greater brilliance. It has a garnet's durability and high
clarity. Tsavorite is often found in pods with a coating of quartz or scapolite,
which the miners call "Potatoes". The green color is due to the vanadium from
the host rock, but some tsavorite is also colored by chromium. It is very rare to find
tsavorite bigger than 5 carats because the heat and pressure which formed tsavorite
millions of years ago shattered most of the crystals. 85% of the mined stones are smaller
than 1 carat, 10% are bigger than 1 carat, 2.5% are bigger than 2 carats, 1% is bigger
than 3 carats. Only occasionally a rough crystal of over 5 carats is found, so that
cut Tzavorites are quite rare and valuable starting from sizes of 2 carats on. The
brilliance and luminosity of the stone are displayed even in smaller sizes.
Tzavorite so desirable? First of all there is its vividly brilliant green. The color scale
shown by Tzavorite ranges from spring-like pale green via intensely bluish green to deep
forest green; colors which have an invigorating and fresh effect on the senses. The
gemstone is also coveted because of its high brilliance. Like all other Garnets it enjoys
an especially high light refraction index (1.734/ 44). Compare a tsavorite with an
emerald. Both gems were formed under conditions of great stress, and are seldom found in
sizes large enough to cut clean stones above two carats. Tsavorite is 200x rarer than
emerald, sells for about 1/4 the price, is more brilliant due to a higher refractive index
(1.74 vs. 1.596 for an emerald) and is harder than an emerald. Finally, 99.9% of all
emeralds are oiled or opticoned and tsavorite is not treated in any way. Tsavorites are
more durable, cost less and are more brilliant than emeralds! Sparks ones
interest doesnt it!
Campbell and Judith Bridges, Tsavorite
Contrary to other gemstones, Tzavorites are not heated or oiled. This is
not necessary for this gemstone. Like all other Garnets it is a piece of immaculate and
pure nature. Another positive characteristic is its robustness. Although showing a
hardness similar to Emerald - about 7 1/2 on the Mohs Scale it is far less
sensitive in its handling. This is not only important for cutting and setting the stone,
but also for wearing. Tzavorite is less likely to become damaged or to splinter even as
consequence of abrupt or incautious impact. It is excellently suited for the favored style
of "invisible setting", where stones are set closely joined, and which cannot be
recommended for Emeralds. Due to its high brilliance, Tzavorite here is an equal match for
the classical stones like Diamond, Ruby and Sapphire.
WHAT TO LOOK FOR
When collecting cut tsavorite, you need to look for an intense vibrant
green color. It should be similar to imperial jade or emerald green. They should be at
least one carat in size and a standard shape. You want to avoid gems that look like
peridot (green/yellow) or stones that are too dark in tone (green/black). Like emeralds,
tsavorite can be green/blue or green/yellow. And like emerald, different collectors have
opposing secondary color preferences. There is no market preference on which color is the
optimum. In AGL terms, it is practically impossible to receive a straight 3.5 color in
emerald; it is similarly as difficult to receive a 3.5 tsavorite. A 4 or 4.5 color
tsavorite is a top gem. Tone should be between 65-85. Average brilliancy should be 50% or
greater. Proportions and finish should be good (6) or better. You do not want 5.5 colors
or 90 tone gems.
Over the past 25 years, Campbell and Judith Bridges have been promoting
and marketing Tsavorite worldwide. Mr. Bridges has written many articles for trade and
commercial magazines, such as JQ, JCK, Colored Stone Magazine, Msafiri Magazine, &
Vogue. He was a speaker at the GIA International Symposiums in 1981 and 1991, lectured at
the Tucson Gem and Mineral Show in 1981, The Precious Stones Congress in Tel Aviv in 1983,
chaired a panel and gave a presentation speech at the International Colored Gemstone
Association Congress in Bangkok in 1987 and was the Kenyan guide and advisor to National
Geographic's correspondent in 1991 for a gem article.
The Gem Forecaster webpage: www.preciousgemstones.com/gffall96one.html
International Colored Gemstone Association web site: www.gemstone.org/gem-by-gem/english/tsavorite.html
Africa's Secret Treasures, Tsavorite From Kenya: http://www.preciousgemstones.com/gfspr02.html#port
Here is where DMS Members
can add their Tsavorite photos to share with us.
Until Next Time
We hope you have enjoyed our visit with
Tsavorite. Please join us next month,
when we expect to see another favored Mineral-of-the-Month!
Until then, stay safe, and happy collecting.
I would like to gratefully acknowledge the generous contributions of our fellow
collectors, authors, curators, professionals, and club members who made this
work possible. Thanks.
© 2006 All contributions to this
article are covered under the copyright protection of this article
and by separate and several copyright protection(s), and are to be used for the sole
enjoying this scholarly article. They are used gratefully with express written
permission of the
authors, save for generally-accepted scholarly quotes, short in nature, deemed legal to
with the appropriate citation and credit. Reproduction of this article must
be obtained by express
written permission of the author, Kenneth B. Casey, for his contributions, authoring,
graphics. Use of all other credited materials requires permission of each
Links and general contact information are included in the credits above,
and throughout this article.
The advice offered herein are only suggestions; it is the reader's charge to use the
contained herein responsibly. DMS is not responsible for misuse or
accidents caused from this
article. Guest authors bear full responsibility for the permissions to reproduce any and
contained herein. All opinions, theories, proofs, and
views expressed within this article, and in
others on this website, do not necessarily reflect the views of the Delaware Mineralogical
About the Author: Karissa is the current President of the Delaware
Mineralogical Society. She is also a member of the Tuscarora Lapidary Society (TLS),
and is an accomplished lapidarist and collector.
She also has
affiliations with other mineral and fossil clubs in the eastern United States, and
encourages folks of all ages on the enjoyment of our hobby.
Invitation to Members
Want to see your name in print? Want to co-author, contribute,
or author a whole Mineral of the Month
article? Well, this the forum for you!
And Members, if you have pictures, or a story you would like to
share, please feel free to offer. We'd like to post them for our mutual enjoyment.
Of course, you get full photo and author credit, and a chance to reach other
collectors, hobbyists, and scientists. We only ask that you check your facts, give
credit where it is due, keep it wholesome for our Junior Members watching, and keep on
topic regarding rockhounding.
You don't even have to be experienced in making a webpage. We
can work together to publish your story. A handwritten short story with a Polaroid
will do. If you do fancier, a text document with a digital photo will suit, as well.
Sharing is the groundwork from which we can get your story out there.
Our club's webpages can reach any person
surfing the net in the world, and even on the International Space Station, if they have a
mind to view our website!
We are hoping for a possible tie-in to other
informative programs upon which our fellow members might want to collaborate.
Contact me with your suggestions.
Our next MOTM will
be a surprise. For 2005-6, we are waiting for your
suggestions. What mineral do you
want to know more about?
Most of the Mineral of the Month
selections have come from most recent club fieldtrips and March Show Themes, and from
inspriring world locales. thus far. If you have a suggestion for a future Mineral of the Month, please e-mail me
at: email@example.com, or tell me at our next meeting.
the Fossil Exposures in the Chesapeake Bay Area" presented by Dr. Lauck
General Club Meeting:
We are meeting at
*Show Committee Meeting, April or May, 2013
*New Home/Lapidary Committee, 2013
*Board Meeting, April, 2013
Next Field Trips
DMS March Show
March 1-2, 2014 at DelTech Stanton
Our 2013 Show
Theme was: "All
That Glitters is as Good as Gold!"
March Show 2013
also commemorates our 50th Show!
It's shiny, yellow, and
is a symbol of 50 Years!Can you guess?
Brook Crick Goethite" by Joe Dunleavy