MICRO
FEATURES
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This page is devoted to inclusions
and those other features of corundum mineral specimens and gemstones which
are best observed under magnification. I am greatly indebted to
friends and colleagues for their generous permission to present their work, creating
this page for all of us to enjoy. |
Please note that there
may be copyright restrictions on these contributions, which must be
respected. Publication here does not in any way compromise the rights
of the owners of this intellectual property. If you desire to
reproduce any of these items, the owner should be contacted directly for
permission. "The Corunduminium", however, does not impose any additional
restrictions on their use. |
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1:
John Koivula Inclusion Photos:
John Koivula, Chief Research Gemologist with the Gemological Institute of
America's Gem Trade Laboratory in Carlsbad, California, has submitted the
following photomicrographs of inclusions and other microscopic features of
ruby and sapphire gemstones. They show another aspect of the beauty
and fascination of gem corundum which cannot be enjoyed without special
equipment in the hands of a special artist. This is a unique gift,
presented for all of us to share, and John has also hinted that every now
and then there might be more! Thank you, John and GIA, for allowing
this unique opportunity! |
Please note that certain
copyright restrictions apply: they are not to be downloaded,
otherwise reproduced, or used in any manner for profit. John's
remarkable book, "Photoatlas of Inclusions in
Gemstones", co-authored with
Dr. Edward Gübelin, may be purchased from the GIA Bookstore in Carlsbad
through the GIA website, www.gia.edu. |
John's captions are given
here alongside the corresponding thumbnails, which you may click on to see
the full resolution photos. Enjoy! |
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Ruby 1:
Polysynthetic
(lamellar) twinning showing the two dichroic colors of ruby in a natural
untreated ruby from Thailand. Magnified 15X |
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Sapphire 1: Growth zoning
in an untreated natural Kashmir sapphire. 15X |
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Sapphire 2: Rutile and
apatite crystals in a natural, untreated sapphire from Rock Creek, Montana.
25X |
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Ruby 2: Corroded
protogenetic calcite crystals in an unheated natural ruby from Mogok,
Burma. 20X |
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Ruby 3: Partially
healed thin film crack decorating a parting plane in a Thai ruby. 80X |
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Sapphire 3: Bright red
crystallites of uranium pyrochlore in a sapphire from Pailin, Cambodia.
25X |
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Sapphire 4: Garnet
inclusion in a sapphire from Songea, Tanzania. 10X |
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Ruby 4: Damaged
primary fluid inclusion in a heat-treated ruby from Madagascar. 20X |
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Sapphire 5: Typical
formation of epigenetic rutile needles in a natural untreated sapphire from
Sri Lanka. 20X |
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Ruby 5: Rutile crystal
with a dislocation "comet tail" in an untreated ruby from Madagascar.
35X |
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Ruby 6: Both
fresh and altered pyrite inclusions in a natural, untreated ruby from Kenya.
15X |
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Sapphire 6:
Sub-metallic rutile prisms in a natural, untreated sapphire from Colombia.
20X |
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Ruby 7: Platinum inclusion in a Chatham Created flux-grown synthetic ruby.
20X |
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Sapphire 7: Platinum
inclusion in a Chatham Created flux-grown blue synthetic sapphire. 20X |
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2: Work
of Feng-Ming Yen: Feng-Ming (Alan)
Yen, a Gem enthusiast from Taiwan, took these photographs of inclusions
in sapphires. Though they are not formally copyrighted, he requests that they are not reproduced or used for
profit without his permission. |
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He sent three pictures of inclusions in Kashmir
sapphires from his personal collection along with the remarks which
follow in quotes.
A positive determination of the composition of these inclusions has not
yet been made. The yellow color in the first is due to the
field illumination. |
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" ... 2 pictures with uraninite inclusions,
I believe, one has a few zircon crystals with uraninite crystals
embedded and the other has stress fracture which (resembles an)
octahedron." [Note: Compare John Koivula's Cambodian "Sapphire 3" above,
which has uranium pyrochlore inclusions. This may be a useful
distinction for origin determination.] |
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"The third picture ..., under 400X,we can see silk like
Ceylon or Burma, but much finer ..." [Note: Only the lines
in direction 10:00 are silk - the thicker lines in the direction 11:30
are striations left from the faceting and polishing.] |
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The pictures below
show minerals attached to small Kashmir sapphires, which may be heat
treated but we are not sure. The crazed greenish to brown material
is being called "melted tourmaline", but its chemical composition has
not yet been ascertained. What do you think? |
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3: Vincent
Pardieu Photographs: Vincent Pardieu is
a French Gemologist living in Southeast Asia, who is particularly fond
of Mogok, Burma. He sent the photos below, showing as yet
unidentified blue crystalline inclusions in Burmese rubies. The
last photo shows the ruby crystal immersed in a fluid with nearly the
same index of refraction as the corundum.
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4:
Dick Berg's Scanning Electron Micrographs:
Dick Berg, Senior Research Geologist, Montana Bureau of Mines
and Geology, took the following SEM's as part of his research into the
formation of Montana sapphires; and he has graciously provided them for
our enjoyment here. They are not copyrighted, and may be copied
with appropriate credit to the source (Dick Berg), but may not be or used for
profit in any manner without his expressed consent. |
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1: Sapphire from the Rock
Creek (Gem Mounatain) deposit, west of Philipsburg, Montana. |
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2: Sapphire from Eldorado
Bar on the Missouri River, northeast of Helena, Montana. |
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3: Sapphire from the
South Fork of Dry Cottonwood Creek (northwest of Butte) showing fresh
fracture. |
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4: Sapphire from South
Fork of Dry Cottonwood Creek showing grooves developed along parting
planes. |
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5: Sapphire from the
South Fork of Dry Cottonwood Creek showing surface texture and grooves
developed along parting planes, both features typical of sapphires from
this locality. |
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6: Sapphire from the Yogo
deposit in central Montana, showing trihedral forms. |
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5: My
Own Closeups: I do not yet have the right
equipment for this, but these crystals are so doggone interesting I
thought you might like to see some of my first puny attempts to record
what you can see under the microscope. Look for these to be
replaced by better ones before too long. Enjoy!
(4/9/04) |
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Two Yogo Gulch, Montana sapphires with prominent surface
etching and "pits" suggesting partial resorption in situ.
Both are about 3/8" in diameter. |
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These two "Yogos" show very unusual pitted and layered
surface textures (loaned by Amos Knapstad, Yogo Creek Mining) |
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Three neat Montana sapphires, given by Marc Bielenberg
to Louis Zara (obtained from his estate). The two on the left are
from Dry Cottonwood Creek, and the one on the right is from Rock Creek. |
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More Yogo shots: On the left are my
two favorite violets. On the right is one with some neat
inclusions (black tourmaline?) |
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Mong Hsu, Burma produces some wild rubies!
On the left are gem crystals with dark blue sapphire cores, the smaller
about the size of rice grains. On the right are "puffed rice" size heat treated "trapiche"
rubies (untreated crystals are often almost black). |
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