Malachite
("Tips and Trips", Volume XXXV/Five May
2006, page 13-14.)
Greetings
everyone. This month I would like to share with you one of the more common
copper bearing minerals - Malachite. Although most commonly occurring in
massive or botryoidal form, Malachite does more rarely occur in some interesting
micro-crystal forms usually as acicular crusts and tufts. Microcrystals
of Malachite are Monoclinic in form and exhibit 2/m crystal symmetry. Micro
crystals of Malachite are acicular and often occur in clusters creating
the appearance of fibrous Masses To the micromount collector Malachite
offers some interesting challenges to find good micro crystals. In the
last few years more good microcrystalline specimens of Malachite have come
on the market. Chemically Malachite is a copper carbonate hydroxide and
is one of the most commonly occurring secondary copper minerals. The name
Malachite derives from the Greek word "Mallow" alluding to the green color
that is similar to a green leafy herb. Although Malachite is generally
known as a green mineral, when in micro crystal form the color varies from
a dark green (sometimes so dark it appears almost black) to a delicate
light green to light blue-green. Shown below in Figure 1 is a photomicrograph
of Malachite as fibrous masses of slender acicular crystals from the Maid
of Sunshine Mine, Gleeson District, Dragoon Mountains, Cochise County,
Arizona. Note the interestingtransition in crystal color from green to
a light blue-green.
Sometimes you can find several crystal forms in one specimen. Figure
2 shown below shows a “jackstraw” arrangement of acicular
Malachite crystals. In most cases, the individual acicular crystals are
actually several smaller crystals arranged in parallel fashion as an acicular
crystalline tuft. This specimen is from the Maid of Sunshine Mine, Gleeson
District, Dragoon Mountains, CochiseCounty, Arizona.
In
some specimens of Malachite several different crystal morphologies can
be seen in close proximity to each other. In the specimen shown in Figure
3 we see a “Jackstraw” arrangement of acicular Malachite
microcrystals placed just above a collection of blocky looking crystals
made up of many slender acicular Malachite crystals all parallel to each
other. The color ranges from dark green (almost black) to a light bluish
green. This specimen is also from the Maid of Sunshine Mine, Gleeson District,
Dragoon Mountains, Cochise County, Arizona. (25X magnification) unaware
of the hidden wonder that can be found even in the most common of minerals
with just a hot mug of tea, some patience, a little careful investigation
and a good stereo microscope. A whole world of wonder lies waiting to be
discovered. I encourage those of you who have not tried mineral micromounting
to give it a try, you will be amazed at what you may discover.
Beryl
("Tips and Trips", Volume XXXIV/Twelve
December 2005, page 7.)
Greetings everyone. This month we will be investigating micromounts
of the mineral beryl. Chemically, beryl is a beryllium aluminum silicate.
There are several varieties exhibiting minor chemical impurities which
cause specific wavelengths of light to be absorbed resulting in a very
strong color to the mineral. Listed below are the most common varieties
of beryl and their colors:
Green: Emerald
Pale Blue: Aquamarine
Red: Bixbite (Also called red beryl)
Pink: Morganite
Greenish-Yellow: Heliodor
Colorless: Goshenite

The
red variety of beryl is the only one that occurs as micro-crystals. The
topaz bearing rhyolite of the Wah Wah Mountains in Utah is the most common
location for red beryl. Although pricy, micromounts of red beryl are readily
available from mineral dealers. There is something almost mystical about
the deep red color of red beryl, particularly when strongly illuminated
under the microscope. The other
colored varieties of beryl are much more difficult to obtain as micromounts.
I have found some very small gemmy crystals of morganite, the pink variety
of beryl in the topaz bearing rhyolite at Topaz Mountain, Utah. These are
rare and you need to break down a lot of material to find one. Aquamarine
is the most readily available variety of beryl, but still difficult to
find in gemmy crystals. Much of the aquamarine specimens I have seen have
been pale blue opaque crystals. By far the real prizes for micromounters
are gemmy crystals of emerald, the deep green variety of beryl. Occasionally
you will find a mineral dealer with good “in matrix”
thumbnail specimens of emerald crystals. These can be broken down to make
some very fine micromounts. However, be prepared to pay a princely
sum for the specimens. Specimens from the Columbian emerald mines afford
the best specimens. Shown at right is a photomicrograph of a gemmy micromount
of emerald from the Muzo Mine in Columbia. (Photographed with Kodak 400
color print film at 50X with white LED illumination – 4 second
exposure.) Although beryl represents a challenge to the micromount
collector, when you find a fine specimen it adds immeasurably to your collection.
At the upcoming mineral shows, I will be prowling the mineral dealer tables
on the look out for some fine beryl specimens for micromounts. See
you there. Until then may all your skies by blue and may all your vugs
be crystal filled.
Legrandite
("Tips and Trips",Volume
XXXV/Two February 2006, Page 8-9)
Greetings
everyone; this month I would lke to highlight one of my favorite micro
mineral subjects, the mineral legrandite. Chemically this mineral is a
hydrated zinc arsenate hydroxide. The type locality for this mineral is
the Flor de Pena Mine, Lampazos, Nueva Leon, Mexico. Current thinking
is that legrandite forms under very special conditions by the action of
arsenic bearing secondary solutions on weathering zinc deposits. This is
a rare mineral being found in only a few localities in the world.
Legrandite is highly sought after by collectors of micro minerals because
of its beautiful straw yellow color and well formed prismatic crystals.
Shown below is a photomicrograph of legrandite on matrix from the Ojuela
Mine, near Mapimi, Durango, Mexico. Notice the Monoclinic prismatic 2/m
crystal habit with the wedge shaped crystal terminations. (Photomicrograph
at 25X with 4 second exposure on ASA 400 film.)
Legrandite
is named after the Belgian mining engineer, Mr. Legrande. The mineral appears
in several crystal habits ranging from slender acicular prismatic crystals
to the large prismatic crystals with wedge shaped terminations shown in
the above photomicrograph. Good specimens of legrandite are hard
to come by on the collector market. Be prepared to pay a princely sum for
good specimens. One of the interesting aspects of legrandite is the prevalence
of sub faces on crystals. In the photomicrograph shown below a small crystal
below the two large wedge shaped crystal terminations. This smaller crystal
shows some of the smaller facets on the crystal termination. (Photographed
at 50X with a 4 second exposure on ASA 400 film.
I have found that Legrandite specimens from the Ojuela Mine near
Mapimi, Durango, Mexico yield the best transparent “gemmy”
crystallized specimens. I have purchased Legrandite specimens from a number
of mineral dealers. Another interesting aspect of Legrandite specimens
from the Ojuela Mine is the complex vuggy matrix on which the crystals
are formed: A complex combination of tubes, stringers and botryoidal masses
with a mind blowing combination of pinks, browns and yellows. Sometimes
I think the matrix is almost as interesting as the mineral crystals. Countless
enjoyable hours can be spent exploring the miniature world under the microscope
with the Ojuela Mine specimens. It is fun sometimes to imagine that you
have shrunk down to a size that would fit on the specimen and are literally
“walking the specimen”.
I would be interested in hearing of your own adventures when exploring
the miniature worlds of micro-minerals. You can reach me at: d.babulski@comcast.net.
Until next month, may all your skies be blue and all your vugs be crystal
filled.
References:
Dana, E.S., A Textbook
of Mineralogy, John Wiley & Sons, Inc, New York, Fourth Edition, Pages
390 - 392.
Grafe, Markus; Nachtegall,
Maartin and Sparks, Donald,
Formation of Metal-Arsenate Precipitates at the Goethite-Water Interface,
Environ. Sci. Technol., 2004, 38, 6561 – 6570.
Lindgren, W., Mineral
Deposits, McGraw-Hill, New York, Second Edition, Pages 99; 871-874.
Internet
References:
http://webmineral.com/data/Legrandite.shtml
http://www.mindat.org/min-2365.html
http://www.xtal-dbeals.com/Ojuela_2.htm
http://10.1911encyclopedia.org/M/MI/MINERAL_DEPOSITS.htm
("Tips and Trips", Vol. XXXIV/nine, September
2005, page 6.)
Erythrite - "Pretty in Pink"
Chemistry: Co3(AsO4)2-8(H2O)
One
of the striking aspects of the mineral world is the large variety of colors
that minerals present. One of the most striking of these colors is
the pink to red of the cobalt arsenate hydrate mineral erythrite. Cobalt
deposits often feature erythrite as a secondary mineral from alteration
of the primary cobalt minerals such as the siegenite (cobalt nickel sulfide)
and linnaeite (cobalt sulfide). This mineral is called "Cobalt Bloom" by
miners and is used to indicate the presence of cobalt ore minerals. Its
pink to red color is distinctive and stands out against the drab coloration
of the host rocks. The mineral gets its name from the Greek, erythros for
"red".
From the micromounters perspective erythrite is somewhat rare but
produces striking specimens. At mineral shows, I have found that this mineral
fetches a princely sum for really good micromount specimens. In micro form
the mineral forms flattened monoclinic form plates, usually a transparent
pink or red color. As
the crystals become larger, the mineral becomes less transparent and deeper
in color. It is interesting that erythrite forms a solid solution series
with the nickel arsenate annabergite. The crystal form for both minerals
is almost the same. The photograph shown below is of erythrite from the
Aghbar Mine, Bou Azzer, Anti-Atlas Mountains, Morocco. The mineral was
photographed through the microscope at a magnification of 30X with Fuji
ASA 200 color print film using a white LED as the light source and a 4
second exposure.
Although good micromount specimens of erythrite are a bit hard to
come by, the beauty and unique color of the mineral makes a must have for
the micromount collection. I have found that the easiest specimens
to obtain and that have good micromount potential are those form the Bou
Azzer area of Morocco.
Until next time may all your skies be blue and may all your vugs
be crystal filled.
("Tips and Trips",
Vol. XXXIV/seven, July 2005, page 5.)
"Those magnificent Copper
Arsenates:"
The element arsenic (As) is located on the Periodic Table of elements
in the same semi-metal band as the elements boron, silicon and tellurium.
As such, the element arsenic exhibits similar characteristics to the other
semi-metals. Silicon for example, when combined with the element
oxygen forms the silicate (SiO2) radical. This unique combination of the
elements silicon and oxygen bonds with a bewildering array of other elements
to form the large number of silicate minerals. Likewise when the element
arsenic is combined with oxygen, it forms the arsenate (AsO4) radical.
Like the silicate radical, this unique combination of the elements arsenic
and oxygen bonds with a large number of other elements (mostly metallic
in nature) to form the large number of arsenate mineral species.
Interestingly enough, the metallic element copper (Cu) bonds readily
with the arsenate combination and forms the bulk of the arsenate mineral
species. For the micromounter this is a fortuitous situation as there are
a number of well-known primary copper mineral deposits
where arsenic bearing hydrothermal fluids have reacted with the
primary copper minerals under oxidizing conditions forming the secondary
copper arsenate minerals. Most of these unique mineral species only crystallize
in micro form. One of more well known of these mineral occurrences
is the Tintic Mining District in Utah and the Antelope Mining District
in Nevada. When more than one of the copper arsenates are present in one
specimen, the color and variety of crystal form is just awesome. In the
Gold Hill Mine in Tooele County, Utah, the copper arsenates conichacite,
strashimirite and mixite occur together in one specimen.
The photographs at right show these three minerals in one specimen.
A careful analysis of this specimen shows that all three of these copper
arsenate minerals did not crystallize at the same time, but most likely
represent subtle changes in the chemistry of the hydrothermal mineralizing
fluids. Strashimitite, which is a copper arsenate hydroxide penta-hydrate,
appears to have been deposited first, followed by conichalcite and then
mixite. Chemically speaking, conichalcite is a calcium copper arsenate
hydroxide and mixite is a bismuth copper
arsenate hydroxide tri-hydrate. The mineralizing fluids appear
to have become enriched in calcium and bismuth as the minerals were being
deposited. What is really cool about these specimens is the conichalcite.
This mineral occurs as bright green spherules. A very close examination
under the microscope of these spherules shows them to be hollow spheres
of conichalcite. It is unknown at this point if the hollow spheres
are actually filled with fluid. It is also interesting to speculate on
how these hollow spherules formed. In this image, ball like
sprays of green acicular strashimirite and light blue mixite populate the
matrix.
In
this image, conichalcte, strashimirite and mixite are all present on the
matrix.
(Both photographs above are courtesy of Dave Babulski from his collection.
They were photographed with Kodak ASA 400 film at a magnification of 25X.
The light source was a white light LED.)
So for some real interesting micromounting adventures you can't beat
those magnificent copper arsenates. Most of the mineral dealers carry copper
arsenates from a variety of localities. Those from the Tintic Mining District
in Tooele County, Utah are among the finest. Until next time, may all your
skies be blue and all your vugs be crystal filled.
("Tips and Trips",
Vol. XXXIV/three, March 2005, page 6.) "CAVANSITE"
This month we will investigate the mineral
CAVANSITE. As mineral species go, cavansite is a relative newcomer,
being officially recognized as a mineral species in 1967. The type
locality is the Owyhee Dam, Lake Owyhee State Park, Malheur County in Oregon.
The host rocks in this area are Miocene volcanics consisting of massive
rhyolite and andesite. The cavansite occurs as minute, rather unimpressive,
crystals in gas cavities in the volcanic rocks. As this mineral occurrence
was rather unimpressive, cavansite was relegated to the status of a mineral
curiosity until the early 1970’s when the mineral was discovered
in the Deccan trap basalts in the Poona district in India. At this locality,
cavansite occurs as well developed spherical aggregates of deep blue crystals
associated with large crystals of stilbite in gas cavities in the basalt.
This mineral occurrence created a sensation in the mineral collecting world.
At mineral shows these days it is not uncommon to see rather awesome large
specimens of stilbite festooned with spherical groups of deep blue cavansite
from the Poona, India locality. The name of this mineral is derived from
its chemical composition of calcium, vanadium and the silicate radical.
The deep blue color is a result of the vanadium content. Good micromounts
of cavansite from the Poona, India locality are very hard to find. You
have to break down some thumbnail size specimens to get at the “Good
Stuff”. The “Good Stuff” is relatively open
radiating clusters of deep blue transparent crystals that occur in the
void areas between large crystals of stilbite. Shown below are some photomicrographs
of some of the “Good Stuff” extracted from thumbnail
size specimens purchased from dealers at the December GMS show. Magnification
is 25X. An
interesting aspect that micromounters have is a visual examination of change
in the intensity of color as the vanadium content in the mineral varies.
Pale blue crystals with deep blue tips are just awesome things to look
at. An examination of the recent mineralogical literature indicates that
most geologists agree that vanadium in cavansitecomes from the host volcanic
rocks. Reports of vanadium content as high as 600 to 750 ppm in the basalts
near Poona have been presented by several geologists working in the area.
Another interesting observation is the sequence of mineral deposition.
Stilbite appears to have been deposited first, followed by cavansite.
In some cases a third depositional phase of heulandite or calcite is observed
as tiny crystals deposited on crystals of cavansite. All in all, some superb
micromounts can be had by having the courage to break down thumbnail size
material. I for one will be looking for some good thumbnail size specimens
of cavansite at the upcoming spring gem and mineral show. There is a real
thrill when you break down a larger specimen and find some of the ”Good
Stuff”. Until next month, may all your skies be blue and all
the vugs you find are crystal filled. (photos by Dave Babulski)
("Tips
and Trips", Vol. XXXIII/9, September 2004, page 10.)
"Vanadinite"
This month we will look at the mineral
vanadinite. In the world of mineral micromounts, vanadinite, with its typical
red color and distinctive crystal forms, is a favorite among mineral micromounters.
I would hazard a guess that just about every mineral micromounter has at
least one vanadinite specimen in their collection. Vanadinite is classed
as a lead chlorovanadate and is the result of the action of vanadium rich
hydrothermal solutions in the oxidation zone of primary lead sulphide deposits.
Vandanite is part of a chemical series with the minerals pyromorphite and
mimetite and these three minerals are sometimes found in the same mineral
deposit. Pyromorphite is a lead chlorophosphate and mimetite is a lead
chloroarsenate. All three of these minerals have very similar crystal forms,
varying primarly only in color. Although the pure form of each is colorless
or very pale yellow, vanadinite is primarily red, pyromorphite is primarily
green and mimetite is primarily yellow. Vanadinite crystallizes in
the Hexagonal-Tripyrimidal form. The most common crystal habits are:
-
Squat tabular hexagonal plates. Crystals
from the Mibladen, Morocco deposits occur in this crystal habit.
-
Hexagonal barrel - shaped prismatic crystals.
Crystals from the Wanlockhead in Dumfrieshire deposit in England exhibit
this crystal habit.
-
Hexagonal prisms with a flat termination
face. Crystals from the Gila Mining District in Arizona show this crystal
habit.
-
Hexagonal prisms with complex pyramidal
termination faces. Vanadanite crystals from the Hamburg mine, Trigo Mountains,
La Paz County, Arizona are famous for transparent "gemmy", deep red prisms
with complex pyramidal terminations. The complex terminations are only
present in micromount size crystals. As the crystals grow larger, the complex
terminations give way to a simple flat face crystal termination.
-
Hexagonal “hopper”
crystals. This is an indicator of very rapid crystal growth and occurs
in most of the vanadinite deposits.
(Photograph by Doug Daniels)
vanadinite crystals, Mibladen,
Morocco from the collection of Doug Daniels. Specimen is approximately
4 cm x 3 cm. |
Vanadinite was first discovered at Zimapan,
Hildago, Mexico and is named for its Vanadium content. I have noted that
most of the Vanadinite seen at mineral shows in the past year is from the
Moroccan mines. Vanadinite specimens from other locations are available
from dealers on the internet and via mail order but you really have to
“dig” for them. An interesting aspect of vanadinite
in micromount form is the reflection of light from inclusions and internal
fractures in the crystal. Although this mineral is primarily red in color,
light reflected internally comes out as yellow. I have found that some
of the vanadinite from the Hamburg Mine, when brightly illuminated looks
like it is on fire! Some of the vanadinite from Mibladen, Morocco when
brightly illuminated shows a beautiful shiller from many parallel reflective
planes in the crystal.
"Wonderful
World of Wulfenite" ("Tips
and Trips", Vol. XXXIII/8, August 2004, page 10.)
This
month's installment of the Micromount Corner will address the "Wonderful
World of Wulfenite". Named after the Austrian mineralogist, Franz Xavier
von Wulfen (1728 – 1805), wulfenite is one of the most sought
after micromount specimens. Officially classed as a lead molybdate,
although other elements can sometimes substitute for lead, providing a
range of mineral compositions. Like the mineral calcite, wulfenite
crystallizes in a number of habits and appears in a wide range of colors
from white to black and a whole range from yellow to red. There is even
a green Wulfenite. This mineral occurs in the oxidized portion of zinc-lead
deposits and as such is often associated with other colorful secondary
lead zinc minerals. Fortunately for the micro-mounter, some of the crystal
habits of wulfenite only occur as micro-crystals. The Fourth Edition of
Dana’s Handbook of Mineralogy has some very nice drawings of
the more common wulfenite crystal habits.
The most common crystal habits are:
-
Thick and thin tabular plates with beveled
edges,
-
Prismatic crystals with pyramidal terminations,
-
Bi-pyramidal pseudooctahedral crystals.
These are usually very small and are exceedingly rare,
-
Thin tabular plates with the corners clipped
forming an octahedral outline, and • Blocky octahedral looking
crystals.
There are enough color and crystal habit
variations on a theme to provide years of collecting for just this one
mineral species. My own micromount collection contains over 150 wulfenite
specimens, and I have just begun to scratch the surface for this species.
Although the type locality is in Austria, the largest producers of wulfenite
specimens are the desert southwest of the United States and Mexico. One
of the best Suppliers of wulfenite mineral specimens is David Shannon Minerals.
Their latest
mineral list has over twenty mineral
occurrences for wulfenite. I have found that ordering thumbnail size
specimens keeps
the cost very reasonable and still
gives me at least two or three good mounts from each thumbnail size specimen.
In the last micro-mount column, I described a way to make accurate crystal
drawings. Wulfenite specimens make excellent drawing subjects as their
crystals tend be a bit larger than the crystals of most other mineral species.
If you are just starting out in mineral micro-mounting, wulfenite makes
an excellent early addition to your collection.
("Tips
and Trips", Vol. XXXV/8, August 2006, page 12 & 13.)Secondary Uranium Minerals – Part 1 Hello everyone, this month the Micromount Corner will begin a series on secondary uranium-bearing minerals. Generally speaking, secondary uranium minerals are brightly colored and make for some striking additions to a micromount collection. This month we will investigate three secondary uranium minerals that are often found together. These are the minerals, meta-uranocircite, schoepite and ianthinite. As is often the case with mineral micromounts, more than one mineral species can be found in a given specimen. Figure 1 is a photomicrograph at a magnification of 30X of the minerals meta-uranocircite, schoepite, and ianthinite. The specimen is from theKrunkelbach Valley Uranium Deposit, Menzenschwand, Black Forest, Baden-Wurttemberg, Germany. The specimen was photographed through the microscope with Kodak ASA 400 color print film with a four second exposure. The microscope light source is a white lightemitting diode.
Figure 1
In
Figure 1, the light green waxy looking mineral is the
meta-uranocircite. Uranocircite is a hydrated barium uranium phosphate.
The meta form is a dehydrated form of the mineral. This mineral is
characterized by its green color and waxy appearance and tabular
crystals that look very similar to the uranium bearing mineral
autunite. The tabular greenish crystal of meta-uranocircite is
surrounded by masses of bright yellow acicular crystals of the mineral
schoepite. This mineral is a uranium oxide hydroxide hydrate and is
highly radioactive. Both the metauranocircite and the schoepite are
deposited on a dark brown resinous botryoidal matrix of the mineral
ianthinite. Ianthinite is a complex uranium oxide deca-hydrate.
All of these secondary uranium bearing minerals are on a light brown
matrix of uraninite. Figure 2 is a closer view of the specimen
photographed at a magnification of 60X
Figure 2 The
Krunkelbach Valley Uranium Deposit was a series of uranium bearing
barite-flourite veins hosted by granite. This deposit was worked until
1990. The dumps have now been removed and the area has been landscaped.
The mineral uranocircite is named for its uranium content and the
Greek for falcon – referring to Falkenstein, Saxony, Germany, where the
mineral is commonly found. The mineral schoepite is named for Alfred
Schoep (1881-1966), Belgian mineralogist who studied uranium
mineralogy. The mineral ianthinite is named for the Greek ianthinos,
“violet” as this mineral often has a somewhat purple coloration.
Mineral species that are alteration products of primary uranium bearing
minerals offer some interesting color and challenges to a micromount
collection. Because these secondary minerals are often highly
radioactive, care must be taken when placing the specimens in your
micromount collection. Some mineral species are very sensitive to radioactivity.
Some collectors house all their radioactive specimens in special
shielded containers. I encourage you to investigate these colorful
mineral species.
("Tips
and Trips", Vol. XXXV/9, September 2006, page 13.)"MIXITE" Greetings everyone, this month I would like to introduce you to a mineral that many micromounters refer to as “the blue-green fuzzies,” so called because the mineral occurs as radial groups of fine hair-like acicular crystals. This is the mineral mixite. On a list of rare minerals, mixite is certainly up near the top. You can count the number of mixite occurrences on the fingers of both hands. In the United States the arsenic bearing mineral deposits in the Tintic District in Utah are the most well known occurrence. Another well known mixite occurrence that yields excellent micromounts is the Majuba Hill Mine in Pershing County, Nevada. This rare mineral species has another distinctionin that it is one of the very few minerals containing the element bismuth.
Chemically, mixite is a hydrated bismuth copper arsenate hydroxide. The mineral forms in the oxidation zone of metal ores that probably contained primary Bismuth Sulfides such as Emplecite or Bismuthinite. Mixite was discovered in 1879 in Czechoslovakia and is named for the Czech mining engineer, A. Mixa.
Color varies from emerald green to blue-green. The fine color and unusual crystal form plus its rarity makes mixite a highly sought after mineral species for micromount collectors.
Most mineral dealers have good specimens of mixite, but be prepared to pay a bit for the really fine specimens. Shown in the photographs below are specimens of mixite crystal spays in vuggy quartz from the Gold Chain Mine, 300 foot level, Mammoth, East Tintic Mountains, Juab, Utah. The specimens were photographed through the microscope at 30X with Kodak ASA400 color print film with a four second exposure.
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