Science Education Center of California

Science Education Center
of California
3001 Chapel Hill Road
Orange, CA 92867
714-292-6845
krawitz@sprynet.com

 

Science Education Center of California

Minerals, Fossils & Gems

 

 

Australian Gold Nuggets

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Locality: 35 miles north of Kalgoorlie, Australia in the Yilgarn gold fields
Composition: Native gold with small quartz and iron stone inclusions

Size: 3.75 inches long; 2.25 inches high; 1.5 inches thick
Weight: 586.8 grams (18.87 troy ounces)
Price: $11,900

Comments: A large and well-shaped gold nugget with small, imbedded quartz pebbles and traces of iron rich clay.

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Locality: Near Kalgoorlie, Australia in the Yilgarn gold fields
Composition: Native gold
Size: 3 inches long; 2.25 inches high; and .75 inches thick
Weight: 337.1 grams (10.84 troy ounces)
Price: $5,600

Comments: A brightly colored nugget that sits well in a vertical direction.

Background: With a density of 19.3 grams/cm3, gold is the heaviest element that can be readily found in nature. Only the heavy platinum metals (platinum, osmium, iridium, and rhenium) have a higher density and nuggets of the platinum group are quite rare. The high density, great malleability and ductility, bright rich color (that does not readily tarnish), rarity and low melting point make gold an ideal metal for use in jewelry, coins, and objects of value.

Gold has been used extensively for over 5,000 years and was utilized extensively by the ancient Babylonians, Assyrian, Sumerian, and Akkadian civilizations. The metal has been used as a form of currency in many countries, and it was not until the early 1930’s that this practice was abandoned. Apparently it took the worlds great leaders several thousand years to discover that a nation’s wealth is based on the quantity of socially useful goods and services that are produced rather than the amount of gold in storage or in a nation’s coinage.

     

Gold from United States Localities

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Left Photo:
Locality: Round Mountain, Nevada
Composition: Crystallized and massive gold with small amounts of quartz impurities.
Size: 3.25 inches long; 1.75 inches wide; 0.75 inches thick
Weight: 200 grams (6.43 troy ounces)
Price: Sold

Comments: This well crystallized gold specimen occurs with small quantities of quartz impurities and is one of the largest pieces of crystallized gold that I have seen from the Round Mountain District.

Center photo:
Locality: Quartzsite, Arizona (Middle Camp)
Composition: Native gold on and in quartz.
Size: 3.5 inches long; 1.75 inches high; 1.25 inches thick
Weight: 219 grams (7 troy ounces)
Price: $750

Comments: A large and aesthetically pleasing specimen from a rare Arizona locality.

Right photo:
Locality: Various
Composition: Native gold
Weight: Most of our small nuggets weigh between 0.5 and 5 grams
Price: $14/gram

Comments: These nuggets are ideal for thumbnail collections and jewelry making.

     

Meteorites

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Iron-Nickel Meteorite
Front, side and bottom views

Crater: Campo del Cielo Crater
Locality: Argentina
Composition: Approximately 90% iron, 7% nickel
Silicate inclusions are occasionally found.
Maximum Dimensions: 12 inches long; 9 inches wide and 7.5 inches high

Weight: 85 pounds
Classification: Coarse Octahedrite
Price: $4,400

Comments: An oriented meteorite with attractive deep pitting and only minor amounts of corrosion.

Background: Meteorites are solid objects that fall to Earth from space. Since meteorites are among the oldest objects that exist on Earth, they provide valuable clues as to the origin and evolution of our solar system and planet. The Campo del Cielo meteorite shown above is a nice example of a well-preserved iron-nickel meteorite that has suffered little in the way of corrosion.

     

California Minerals

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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 as follows:

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.
Price: $300

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.
Price: $295

     

Malachite from United States Localities

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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
Price: $295

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
Price: $275

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.

     

Gem Azurite

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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
Price: $395

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.

     

Malachite & Azurite from the Congo

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All photos:

Locality: African malachite mixed with azurite (Congo)
Composition: Mixture of hydrous copper carbonates Cu2(CO3)(OH2) and Cu3(CO3)2(OH)2.
Dimensions: Various sizes (click on photo for larger image and detailed size comparison)

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.

     

Malachite Stalactites

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All photos:
Locality: The Congo and Bisbee
Composition: Malachite

Dimensions: Various sizes (click on photo for larger image and detailed size comparison)
Price: Variable depending on shape and quality. Most of the African stalactites and botryoidal masses are around $20 - $40 per pound. Perfect specimens with extraordinary shapes (and few surface scratches) command higher prices and are individually priced. The material from Bisbee generally goes for around $100/pound. The best material from Bisbee is priced individually. Fine specimens are costly.

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.

     

Fossils

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Locality: Morocco
Composition: Fossilized ammonite (calcite replacing organism)

Dimensions: 19 inches long; 15 inches wide, and 6 inches thick
Price: $900

Comments: A large and finely detailed ammonite with minor repair work and reconstruction.

Locality: Florida
Composition: Natural coral composed mainly of calcium carbonate.

Dimensions: 14.5 inches long; 5 inches wide, and 2 inches thick
Price: $95

     
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Locality:   Madagascar
Composition:   Calcite replacing an ammonite.
Sizes:   1 to 4 inches in diameter. Larger sizes are available but are less abundant.
Prices:   Our smallest ammonites available (most economical in price) are about ½ inch to ¾ inches across and are currently priced at $2/slice. Larger sizes are available and are priced at around 10 cents a gram, or around $100/kilogram. Based on these prices, museum quality items (as nice as those pictured in textbooks and several inches in diameter) can be purchased for around $30 - $75 dollars per slice. Occasionally we will have even larger ones (well crystallized and almost a foot in diameter with spectacular colors) for around $200 per slice. The largest ones are used in the science museum on wheels presentations and are occasionally sold as we obtain duplicate material.

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.

     

Cut Stones

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Left photo:
Locality: Brazil
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.
Price: The specimens shown above have already sold and typically sell for around 1 to $4/carat.

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.

     

Crystallized Metallic Minerals

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Left photo:

Locality: Viloca Tin Mine (La Paz District) Bolivia
Composition: Tin Oxide (SnO2)
Dimensions: 5 inches long and 5 inches wide
Price: $695

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.

Center photo:

Locality: Baia Sprie, Romania
Composition: Antimony sulfide (Sb2S3)
Dimensions: 5.25 inches wide and 4.5 inches tall
Price: $895

Comments: A museum sized cluster of acicular stibnite crystals from a classic European locality.

Right photo:

Locality: Province: Hunan
Region: Lou Di
City: Leng Shui Jiang
Mine Name: Xi Kuang Shan (Tin Mineral Mountain)

Composition: Antimony sulfide (Sb2S3)
Dimensions: 1 to 2 inch long acicular crystals without matrix
Price: $5 to $15 each

Comments: These thumbnail specimens make ideal gifts, and can be used as teaching tools to demonstrate the appearance of metallic surfaces and crystal growth.

     

Native Copper

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Left Photo:
Locality: Chino Mine, New Mexico
Composition: Native copper (Cu)

Dimensions: 14 inches long and 7 inches wide
Price: $115 (Sold)

Center Photo:
Locality: Chino Mine, New Mexico
Composition: Native copper (Cu)

Dimensions: 2 – 4 inches wide and 3 - 4 inches tall
Price: $28 - 40 (Sold)

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.
A trace element essential to many plants and animals. Occurs in biological complexes such as pheophytin (analog of chlorophyll), hemocyanin, tyrosinase and ceruloplasmin.

Uses: Manufacture of bronzes, brass, other copper alloys, electrical conductors, ammunition, copper salts, works of art and in coinage. We should note that the copper coins of today are mostly zinc. After the year 1982, the United States Mint changed the composition of the U.S. cent to 97.5% zinc and 2.5% copper. These zinc cents have a coating of pure copper and were designed to reduce the cost of coinage and save the critically important element for more pressing needs. Zinc is not only less expensive than copper, it is also about 100 times more abundant than copper in the Earth’s crust.

Sources
  1. The Merck Index (12th Edition), Pg. 426
  2. Sienko, Michell J., and Robert A. Plane. 1966. Chemistry: Principles and Properties, McGraw-Hill Book Company.
     

Amethyst

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Left Photo:
Locality: Brazil and Uruguay
Composition: SiO2 (Quartz with traces of ferric iron)

Dimensions: 4 inches long and 3 - 4 inches wide
Price: $8 - $15 for pieces of the type shown above

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.

Center Photo:
Locality: Brazil and Uruguay
Composition: SiO2 (Quartz with traces of ferric iron)

Dimensions: Most amethyst slabs range from 1 to 10 square inches in area
Price: $8 - 40 (Sold)

     

Quartz Crystals from Brazil

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Left Photo:
Locality: Brazil
Composition: Quartz with inclusions of chlorite and rhodonite

Dimensions: 5 inches tall and 4 inches in diameter
Price: $395

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.

Center Photo:
Locality: Brazil
Composition: Quartz (Var. rock crystal: SiO2)

Dimensions: 8.5 inches tall and 6 inches wide
Price: $395

Comments: A nice and well-crystallized rock crystal cluster that has not been buffed up or polished.

     

Assorted Crystals

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Left photo:

Locality: Afghanistan
Composition: Lapis lazuli crystal in marble (Na,Ca)8(Al,Si)12O24(S,SO4)

Dimensions: 5 inches long and 3 inches wide
Price: $150

Comments: A well crystallized Lapis lazuli crystal in a marble matrix.

Center photo:

Locality: Yao Gan Xian Mine, Hunan Provance China
Composition: Fluorite (CaF2)

Dimensions: Crystal clusters (1 – 2 inches across)
Price: $8 - $19 each

Comments: An inexpensive way to start a colorful mineral collection.

Right photo:

Locality: Bombay Quarry (Bombay, India)
Composition: Gyrolite (Na,Ca)16 (Si23Al)O60(OH)5 .15H2O

Dimensions: 4 inches wide and 5 inches tall
Price: $95

     
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Left photo:

Locality: Mid Continent Mine (Treece, Kansas)
Composition: Sphalerite (ZnS) on dolomite CaMg(CO3)2

Dimensions: 5 inches long and 4 inches tall
Price: $39 (Sold)

Comments: A nice Tri-State sphalerite on a dolomite matrix.

Center and right photos:

Locality: Peru
Composition: Pyrite (FeS2)

Dimensions: Crystal clusters (Approximately 1 – 3 inches across)
Price: $10 - $20 each

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.

     

Fluorescent Minerals

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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:
  • Scheelite (fluorescent blue)
  • Hardystonite (fluorescent purple)
  • Anglesite and cerussite (fluorescent orange)
  • Halite (fluorescent red)
  • Sapphire (blue and red fluorescence)
  • Zircon (orange fluorescence)
  • Adamite (lemon-yellow)

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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