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Monazite-(Ce) from
the Siglo XX mine,
Llallagua, Bolivia
Monazite gets its name from
the Greek word "monazein", which means "to be alone", in allusion
to its isolated crystals and their rarity when first found. Typically
the various species of Monazite are found in granitic pegmatites,
but recently, a remarkable discovery of some of the most vibrant
and attractive crystals of Monazite was made at the historic and
world famous Siglo XX mine in Llallagua, Bolivia. This mine is renowned
for its phosphate species, and Monazite is among the most highly
sought after among collectors. The crystals at Siglo XX are found
in hydrothermal tin veins where there is almost a complete absence
of Thorium (usually a trace element in Monazite). This
contributes to the brighter color of these crystals. I have labeled
these specimens as Monazite-(Ce), as I had a few specimens
analyzed, and all of them came back with just a slight amount of
Thorium present.
It has been reported to me that certain pieces of this material
show zero Thorium content whatsoever, and thus have been labeled
as Monazite-(Nd). Without analyzing each individual specimen, one
cannot be certain of the true identity of all the pieces in this
update, so Im staying on the safe side and labeling them all as
Monazite-(Ce).
Below is the entry for Monazite from
Mark Chance Bandy's famous book, Mineralogy of Llallagua, Bolivia
which was published in 1944, and is still very applicable to
this day.
1976 TGMS
These specimens represent the finest examples of the species
that I have seen from this mine, and arguably any other mine due
to the fact that they form in beautiful butterfly, heart or
X-shaped twinned crystals (twinned on {100} and often
interpenetrating), on gem quality Quartz crystal matrix.
Typically, Monazite occurs in somber colors, i.e., brown, and are
often opaque, whereas these crystals are translucent to gemmy and
bright in appearance. Perhaps the most intriguing aspect of these
specimen is that they exhibit an evident color change effect in
different lighting. The hue of the crystals range from orange-pink
in incandescent and sunlight, to a dull yellow or whitish-yellow
color in certain fluorescent lighting and spiral energy saver
bulbs. The change in color is very appealing, and we have illustrated
this phenomena below as an example. **Please note that these specimens
do not photograph exactly true to color, because the camera has
great difficulty capturing the subtleties of the hues, so please
keep this in mind when viewing the photos below.
 
(Above photos taken in
sunlight)
 
(Above
photos taken under
spiral,
mercury-bearing "energy saver" light bulbs)
Aside from Quartz, the only significant associated species with
this material is Xenotime. These crystals are typically 1-2 mm,
with a simple tetragonal prismatic habit, and also display a color
change ranging from a pale greenish-yellow in incandescent and sunlight,
but show a strong reddish-orange color under spiral energy saver
bulbs. I have only ONE confirmed specimen in this lot with a Xenotime
association, but that is not to say that other pieces might also
have Xenotime crystals present which I could not see.
Lastly, it must be noted that Monazite is not often found in such
well-crystallized display specimens such as these new pieces from
Siglo XX. It is often the case that Monazite crystals are found
either embedded in matrix, or as single or floater crystals off
matrix. The crystals on these specimens (some of which exceed 1
cm.) are certainly the largest I have seen from this locality, and
the fact they are prominently sitting atop highly desirable Quartz
crystal matrix and are not at all buried, makes them all the more
attractive. This is a great opportunity for collectors to obtain
an excellent Monazite specimen from one of the most storied localities
in the world.
Enjoy !
No.
Mon 12081
Monazite-(Ce) -
$2500
This
the best large cabinet specimen of this material that I have
seen. Possibly the best large cabinet Monazite from this mine
extant. The piece is simply loaded with dozens upon dozens on
superb quality, sharp, lustrous, translucent butterfly or
X-shaped twinned crystals of pinkish-orange Monazite-(Ce)
sitting atop gemmy, prismatic colorless Quartz crystals on matrix.
Admittedly, the piece could use a trim, and the specimen honestly
looks much better in person than the photos indicate. For the
size of the piece, the quality of the crystals, and overall
visual appeal, this is a significant phosphate specimen from
any locality.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 15.2 x 11.2 x 7.3 cm.
Largest Crystal: 1.0 cm.
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No.
Mon 12082
Monazite-(Ce) -
$200
A
good reference piece featuring a few sharp, lustrous, gemmy,
pinkish-orange color twinned crystals with gem/gemmy Quartz
crystals on matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 7.3 x 4.8 x 3.2 cm.
Largest Crystal: 0.5 cm.
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No.
Mon 12083
Monazite-(Ce) with Xenotime -
$250
(SOLD)
A
nice full-size miniature specimen featuring a few scattered,
pinkish-orange color heart-shaped twinned crystals of Monazite-(Ce)
associated with a few small (1 mm+), gemmy, prismatic, tetragonal
crystals of Xenotime which exhibit a color change from pale
greenish-yellow in incandescent lighting to a reddish-orange
hue under spiral energy saver bulbs. This is the only piece
that I can say for certain has Xenotime crystals on it, but
other pieces in this update may have associated Xenotime as
well.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.3 x 4.2 x 2.5 cm.
Largest Monazite Crystal: 0.5 cm.
Largest Xenotime Crystal: 1 mm+.
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No.
Mon 12084
Monazite-(Ce) -
$600
A
nice display specimen with several orange-pink, sharp, lustrous,
twins (plus some multiple twins) of Monazite-(Ce) perched upon
gem quality, thin, prismatic Quartz crystals on matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 6.5 x 4.7 x 3.0 cm.
Largest Crystal: 0.9 cm.
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No.
Mon 12085
Monazite-(Ce) -
$650
A
remarkable piece for a smaller specimen. In all honesty, this
piece should be trimmed down to a top notch thumbnail, because
it would only accentuate the already large crystals on the specimen.
There is a beautiful X-shaped twin on this piece (the best
photo of it is pictured at the top of the page where I showed
the color change photos) which is accompanied by a larger twinned
crystal group. For the quality and beauty of the piece, it surely
is one of the best pieces pound for pound in this update.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 3.6 x 2.3 x 1.8 cm.
Largest Crystal: 1.1 cm.
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No.
Mon 12086
Monazite-(Ce) -
$300
An
fine little toenail specimen with a good amount of translucent,
lustrous, sharp, "X"-shaped, twinned, pinkish-orange crystals associated
with water-clear thin crystals of Quartz on matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 3.5 x 2.8 x 2.4 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 12087
Monazite-(Ce) -
$550
(SOLD)
This
small miniature specimen hosts a few gorgeous twinned crystals
of Monazite-(Ce) with excellent luster, translucency and sharpness
sitting on glassy, transparent Quartz crystals on matrix. The
main X-shaped twin on this piece is especially nice, and they
are some of the largest crystals in the lot.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 4.1 x 4.0 x 2.2 cm.
Largest Crystal: 0.9 cm.
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No.
Mon 12088
Monazite-(Ce) -
(SOLD)
This
piece is loaded with dozens of gorgeous butterfly wing-shaped
or rabbit ears-shaped twinned crystals of Monazite-(Ce). The
crystals on this specimen are very rich in color and have excellent
sharpness, luster and translucency. The upper portion of the
specimen features a few sharp, striated cubic crystals on Pyrite
which along with the Monazite crystals are sitting atop slender,
gem quality, colorless, hexagonal prisms of Quartz on porphyry
matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.1 x 4.0 x 2.6 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 12089
Monazite-(Ce) -
$275
(SOLD)
Several
attractive, lustrous, sharp, butterfly and X-shaped twinned
crystals of Monazite-(Ce) sit amongst water-clear, colorless
Quartz crystals on this good-looking miniature size display
specimen.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 4.6 x 3.1 x 2.3 cm.
Largest Crystal: 0.5 cm.
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No.
Mon 120810
Monazite-(Ce) -
$275
Here
we have a good miniature specimen from this find. It hosts several
fine, sharp, lustrous, translucent, pinkish-orange twinned crystals
including a beautiful pair of butterfly twins as illustrated
in the close up photo.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 4.4 x 3.8 x 3.1 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 120811
Monazite-(Ce) -
$200
A
very good representative specimen of this material featuring
a few fantastic little X-shaped twinned crystals of a pinkish-orange
color with good luster and sharpness. The piece was not the
easiest to photograph, but certainly is a good buy for the quality
and size of the crystals.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.1 x 4.6 x 2.6 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 120812
Monazite-(Ce) -
$150
This
specimen features a few isolated, sharp, lustrous, orange-pink
color X-shaped twinned crystals of Monazite-(Ce) associated
with thin, sharp, transparent colorless Quartz crystals on porphyry
matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.2 x 3.2 x 2.4 cm.
Largest Crystal: 0.7 cm.
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No.
Mon 120813
Monazite-(Ce) -
$425
This
is certainly one of the best buys in the lot due to the fact
that it features a very sculptural multi-twinned crystal of
Monazite-(Ce) that measures nearly a full centimeter, which
is huge for this locality. The piece could be trimmed down a
bit to reduce the crystal to matrix ratio, but its still a
very good specimen and would certainly make many collectors
happy just the way it is.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 6.4 x 5.3 x 2.7 cm.
Largest Crystal: 0.9 cm.
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No.
Mon 120814
Monazite-(Ce) -
$300
Several
lustrous, sharp, twinned crystals of pinkish-orange Monazite-(Ce)
crystals are packed into the upper portion of this specimen.
The piece has more crystals than almost any other specimen
in the update, which leads me to believe that it formed on the footwall
of the pocket where the solution was more concentrated.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 6.7 x 4.5 x 2.7 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 120815
Monazite-(Ce) -
$350
This
small cabinet specimen hosts a handful of fine, sharp, lustrous,
translucent, pinkish-orange twinned crystals sitting atop gem
quality, needle like Quartz crystals. The fact that the Monazite
crystals are fairly isolated is a nice tough, and you can clearly
see the beautiful pair of butterfly twins illustrated in the
close up photo.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 7.1 x 6.4 x 4.0 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 120816
Monazite-(Ce) -
$250
This
is a wonderful large miniature specimen featuring a very eye-catching,
isolated, multi-twinned crystal group of Monazite-(Ce) on Quartz
crystals on matrix. This cluster of twinned crystals is one
of the largest in the lot, and as you can see in the photos,
its a really beautiful group that makes it one of the best
smaller pieces in this lot.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.3 x 3.3 x 2.3 cm.
Largest Crystal: 0.9 cm.
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No.
Mon 120817
Monazite-(Ce) -
$150
This
specimen hosts a single, light pinkish-orange color multi-twinned
crystal cluster of Monazite-(Ce) in a nest of white, gemmy,
prismatic Quartz crystal matrix. A perfect specimen for any
collector who prefers to have isolated crystals on matrix. In
my experience, it is very difficult to obtain specimens like
this with one twinned crystal group on matrix.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 5.0 x 3.3 x 2.5 cm.
Largest Crystal: 0.6 cm.
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No.
Mon 120818
Monazite-(Ce) -
$700
This
piece is loaded with several very good sized, blocky, sharp,
pinkish-orange color, X-shaped, heart-shaped and butterfly
twinned crystals on Monazite which are densely packed against
a matrix of gemmy prismatic grey to colorless Quartz crystal
matrix. This specimen displays beautifully and theres a lot
of Monazite crystals on this one. For the size and aesthetic
beauty, this is definitely one of the better specimens of this
material that I have seen.
Locality: Contacto vein, Siglo XX mine, Llallagua, Bustillo
Province, Potos Department, Bolivia
Specimen Size: 6.7 x 3.7 x 2.9 cm.
Largest Crystal: 0.7 cm.
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