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| At the Science Education Center, a great deal
of effort has gone into acquiring a large number of local minerals,
and historical items relating to California’s early history.
This collection is always changing due to frequent sales and
acquisitions. Two such items are shown above and are described
Left photo: Azurite and malachite
together (gem quality and not stabilized) from the Copper
World Mine (San Bernardino County). Note: A repaired specimen
from the Dr. Ralph Pray collection.
Right photo: A 3 pound piece of botryoidal
nephrite from Jade cove, California. This 6 inch long cabinet
specimen has good color and some translucence.
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|Locality: Prince of Wales Island, Alaska
Composition: Hydrous copper carbonate Cu2(CO3)(OH)2
Dimensions: 5 inches long; 4 inches wide,
and 2.25 inches high
Comments: A rare malachite specimen from the Dr. Ralph Pray collection. Dr. Pray was the Territorial Assayer for the Alaskan Territories in 1957.
|Locality: Baghdad, Arizona
Composition: Malachite with drusy chrysocolla
Dimensions: 5 inches long; 4.5 inches wide,
and 4 inches high
Comments: A colorful drusy chrysocolla specimen on a malachite matrix. The drusy chrysocolla portion can be cut from the specimen and used in jewelry.
Background: Malachite derives its name either from the Greek word malachos (for soft) or from the mallow by virtue of its green color. Malachite is an important copper ore and forms in the upper oxidized zones of copper deposits. When free of matrix, malachite is often suitable for cutting and is used as a valuable ornamental stone.
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|Locality: Morenci, Arizona
Composition: Hydrous copper carbonate Cu3(CO3)2(OH)2
Dimensions: 7 inches long; 5 inches wide,
and 1.25 inches thick
Comments: This azurite specimen contains over 2,500 grams of gem quality azurite which can be used as a museum displayable cabinet specimen or as cutting rough for jewelry. Unlike most azurite that is on the market, this piece has not been chemically stabilized or enhanced with waxes or resins.
Background: Both malachite and azurite are found in the upper oxidized zones of copper deposits and are important indicators of copper. Azurite is less chemically stable than malachite and tends to slowly covert into malachite over time. This can be observed in malachite pseudomorphs after azurite which have the crystal structure found in azurite specimens and the green color of malachite.
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Locality: African malachite mixed with azurite
Price: With the exception of the small pieces in the lower right photo (typically $5 to $15 each), most specimens are priced in the $40 to $150 range. Larger specimens (not shown) are costly and are a few hundred dollars. The malachite ashtray (lower left photo) sold for $120.
Comments: Some very colorful combinations of malachite and chrysocolla have been mined recently in the Congo. The specimens shown here were part of a larger group (about 10 specimens) that we had recently purchased. Unfortunately, they sold even before we could get the photos on line. As a result, the specimens shown above should be characterized as a representative sample of the material that we can get from time to time.
To satisfy the needs of our mineral enthusiasts, we have over 100 specimens of copper minerals to choose from and have ready access to a number of mining localities. As always, it is best to call in advance to get a latest update on what is available.
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Locality: The Congo and Bisbee
Dimensions: Various sizes (click on photo
for larger image and detailed size comparison)
Comments: These specific specimens have already been sold. We have a good collection of botryoidal malachite masses and stalactites in stock. The specimens shown above are a representative sample of the quality available at the Science Education Center.
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| Locality: Morocco
Composition: Fossilized ammonite (calcite replacing organism)
Dimensions: 19 inches long; 15 inches wide, and 6
Comments: A large and finely detailed ammonite with minor repair work and reconstruction.
Composition: Natural coral composed mainly of calcium carbonate.
Dimensions: 14.5 inches long; 5 inches wide, and 2
Comments: The Science Education Center features over 1,000 cut and polished slabs (500 pairs) of very well preserved fossilized ammonites. Most of the ammonites have a complete outer shell, and show in great detail each of the chambers that the living creature has occupied. Many of the chambers have hollow portions filled with calcite crystals (yellow) and iron rich impurities (red). Each ammonite is unique in its spiral detail, extent of chamber preservation, and mineral contaminants that are responsible for the vivid yellow and red colors.
Background: Ammonites were abundant members of the mollusk family in the Mesozoic era, some 100 million years ago. The present-day nautilus may be a descendant of these long-extinct marine animals. Ammonites built their multi-chambered shells out of calcium carbonate. Through the millennia, this originally fine-grained material has been recrystallized until now it is virtually a marble yet still preserving the shape and pattern of the dead animal's house.
Services: The growing popularity of ammonites in jewelry (earrings and necklaces) has led to an increased demand, which occasionally outstrips the available ammonite supply. To meet the needs of the jewelry market, we are offering to drill small holes in thin slices to accommodate chains, bezels and other jewelry attachments. The cost of this service (for ammonites purchased from the Science Education Center) is only $1/hole.
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Composition: Amethyst, citrine and smoky quartz.
Carat size: Our large specimen stones usually
range from a few carats to several thousand carats. We have
a smoky quartz (sale pending) that weighs approximately 4,750
carats. It was so big that the GIA in Carlsbad had to weigh
it on their postal scale instead of their standard gem scale.
Comments: The Science Education Center generally does not specialize in cut stones. There are a large number of companies that specialize in color stones and some have very good prices. From time to time, we pick up a super deal and will pass it on to our customers. The specimens shown above were part of such a purchase and are a representative sample of the size and quality of the material that we occasionally have in the 1 to $4/carat price range. Usually after the Tucson show, a few cut stones will be acquired, either individually or as part of a larger acquisition. Give us a call in mid February to see what we have picked up. Specific requests for items should be made by early December.
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Locality: Viloca Tin Mine (La Paz District)
Comments: A well crystallized Bolivian cassiterite on a matrix of quartz crystals. The smaller specimen to the right of the Bolivian cassiterite is a one pound single crystal of cassiterite from China. This purplish-brown specimen is from the collection of Clifford J. Krueger, and is priced at $400.
Locality: Baia Sprie, Romania
Comments: A museum sized cluster of acicular stibnite crystals from a classic European locality.
Locality: Province: Hunan
Comments: These thumbnail specimens
make ideal gifts, and can be used as teaching tools to demonstrate
the appearance of metallic surfaces and crystal growth.
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Dimensions: 14 inches long and 7 inches
Dimensions: 2 – 4 inches wide and
3 - 4 inches tall
Comments: Native copper, copper carbonates (malachite and azurite), natural alloys of copper and silver, and copper combined with other minerals (such as calcite) are a favorite at the Science Education Center. We have over 100 specimens of copper minerals to choose from and have ready access to a number of mining localities. As a result, we generally do not run out of copper specimens. As always, it is best to call in advance to get a latest update on what is available.
Background on Copper: Occurrence
in the earth’s crust: 70 parts per million; also present
in seawater: 0.001 – 0.02 ppm. Two naturally occurring
isotopes: 63 (69.09%), 65 (30.91%); nine artificial isotopes:
58 – 62, 64, 66-68. One of the earliest known metals.
Besides native copper, which can be as high as 99.9% pure,
the element occurs as two principal classes of minerals: sulfide
ores and oxide ores. The principal sulfide ores are calcocite
(Cu2S), calcopyrite, or copper
pyrites (CuFeS2), and covelite
(CuS); the principal oxide ores are cuprite and tenorite,
and the major carbonate is malachite (Cu2(CO3)(OH)2).
About 80% of the present annual copper production (around
3,000,000 tons per year) is from the sulfide ores.
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Dimensions: 4 inches long and 3 - 4 inches
Comments: The Brazilian and Uruguayan amethyst can generally be distinguished by the intensity of the color. The Uruguayan specimens tend to have smaller crystals and a much deeper purple color than their Brazilian counterparts. The deeper colors are also more highly sought after. As a result, the prices tend to be considerably higher for the Uruguayan material. We have many small pieces for under $15 and a few museum items (on occasion). Our current giant is 98 pounds ($675) and has a large calcite crystal extending through the center of the druse.
Dimensions: Most amethyst slabs range from
1 to 10 square inches in area
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Dimensions: 5 inches tall and 4 inches
Comments: A fascinating specimen of chlorite and rhodonite entombed in rock crystal.
Note: The crystal faces have been cleaned up a bit to bring out the beauty of the multiple mineral inclusions. Finally, some of the internal inclusions display very colorful irises, which are visible in natural and artificial light.
Dimensions: 8.5 inches tall and 6 inches
Comments: A nice and well-crystallized rock crystal cluster that has not been buffed up or polished.
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Dimensions: 5 inches long and 3 inches wide
Comments: A well crystallized Lapis lazuli crystal in a marble matrix.
Locality: Yao Gan Xian Mine, Hunan Provance
Dimensions: Crystal clusters (1 –
2 inches across)
Comments: An inexpensive way to start a colorful mineral collection.
Locality: Bombay Quarry (Bombay, India)
Dimensions: 4 inches wide and 5 inches
Locality: Mid Continent Mine (Treece, Kansas)
Dimensions: 5 inches long and 4 inches tall
Comments: A nice Tri-State sphalerite on a dolomite matrix.
Center and right photos:
Dimensions: Crystal clusters (Approximately 1 – 3 inches
Comments: We have a large quantity of well-crystallized pyrites for the beginning collector. Children can measure the size of each crystal face as well as the angle between crystal faces. By finding the sum of all crystal face measurements and dividing by the total, the student can determine the average value for the crystal face size. Students can then do the same thing for the angles between crystal faces and check to see which one varies more, the crystal sizes or the angles between crystal faces.
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| The Science Education Center has over 2,000 pounds
of fluorescent minerals composed mainly of willemite (fluorescent
green) and calcite (fluorescent red). Many of the specimens
contain rare and colorful minerals such as zincite and the typical
black franklinite. Scarce fluorescent minerals at the Science
Education Center (several in the photo above) include crystals
of the following:
Prices: We obtained a large quantity of fluorescent minerals at very reasonable prices. As a result, most specimens can be obtained for around 2 to 6 dollars per pound. Cut fluorescent spheres are remarkably attractive and command prices in the $100 - $600 range. The rarer mineral crystals (not massive material) are individually priced and range from a few dollars to several hundred dollars for museum specimens. The items shown in the photograph contain both fluorescent crystals as well as the typical massive material, which is rather modestly priced.
What is fluorescence: With the exception of the rare fluorescent minerals, most of the fluorescent material in the Krawitz Collection comes from the contact metamorphic zinc deposits at Franklin and Ogdensburg, Sussex County, New Jersey. This great zinc deposit has yielded a fortune in zinc for the New Jersey Zinc Company, and a bonanza of fluorescent material for collectors and museums.
The main fluorescing minerals in this great zinc deposit are willemite (Zn2SiO4) and calcite (CaCO3). Willemite will fluoresce an eerie greenish yellow and calcite will fluoresce a bright red. The fluoresence is due to the ability of electrons in these minerals to go to a higher energy state when illuminated by higher energy light, which in this case is short wave ultraviolet light (254 nm). When the excited electrons fall back to the lower and stable energy state, energy in the form of visible light is emitted. Some of the finest fluorescence is found in the fluorescent spheres, which are available for viewing and sale at the Science Education Center.
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