Rock Picture of the Week Archive 6

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Barite
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Barite, or Baryte,  (BaSO4) is generally found in sedimentary rocks and is the primary source of barium. It is also used as a weighting agent in drilling wells, a pigment in paint, and a medical agent for taking xrays of the intestines.
Barite is too soft to be effectively used as jewelry.



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 Bixbyite
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Bixbyite ((Mn,Fe)2O3) is a manganese iron oxide. The amount of iron in the formula varies greatly. This specimen came from Thomas, Utah.
It is submetalic, opaque, and is fairly rare. The main use of Bixbyite is as specimens.

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Creedite
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Creedite (Ca3Al2F4SO4(F,OH)4-2(H2O)) is a fairly rare mineral found in oxidized ores, usually associated with Fluorite. It is named for the Creed Quadrangle, Colorado, where it was discovered.
The color is generally a shade of purple and it is too soft to be used in jewelry.

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Sulfur
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Sulfur, or Sulphur, (S) is a common element and mineral. It is very reactive and exists in combination with many minerals. Some life forms use it instead of oxygen to sustain life.
Native Sulfur makes an attractive specimen, but can easily be damaged by temperature changes, moisture, or rough handling.

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Selenite
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Selenite (CaSO4-2H2O) is the name often given to the crystalline form of Gypsum. It is common in sedimentary formations, especially where seas or lakes have evaporated.
Although the crystals are very attractive, they are too soft to be used in jewelry.

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Aquamarine Tourmaline and Quartz
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Aquamarine (Be3Al2Si6O18), the long bluish crystals, Tourmaline, or Schorl (formula complicated and variable) are the dark crystals, and Quartz (SiO2), the pale smokey crystals, make up this attractive specimen from Erongo, Namibia.

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Vanadinite and Magnesite on Barite
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Photo by Jim Bryan

From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

This specimen contains red/orange Vanadinite (Pb5(VO4)3Cl), and brown Magnesite (MgCO3), on white Barite (BaSO4). This one came from Morocco.

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Pyrite
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Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Pyrite (FeS2) is a very common sulfide mineral found in many different types of rock formations. These cubes are about an inch wide.
The name is derived from the word "fire", because it will create hot sparks when struck by iron or a harder rock.
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Mortar and Pestle
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Photo by Jim Bryan

This mortar with pestle is about 10 inches wide and is made of sandstone, but they were made in many sizes and from different materials.
The Native Americans used them mainly for food preparation.

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Limestone Fence Post
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Photo by Jim Bryan

In some areas of the US Midwest wood for fence posts was scarce. Some settlers used the readily available limestone formations for their materials.
This is just the upper portion of a limestone post. The grooves on the left are drill holes, and the ones on the right are where the fence wires sat. I was told that in the winter they poured water in the drill holes and when it froze the ice expanded, cleaving the post off of the formation.

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Fluorite
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Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Fluorite (CaF2) is named for its tendency to flow at high temperatures. It is used as a flux in smelting iron.
Fluorite has a hardness of 4 and is used as a standard for the Mohs hardness scale.

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Rhodochrosite and Pyrite
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 Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Rhodochrosite (MnCO3), a minor ore of manganese, and Pyrite (FeS2), a minor ore of iron, make an attractive contrast in this specimen. Both minerals are sometimes used for ornamental purposes.
This one came from China.



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Chalcanthite
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 Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Chalcanthite is hydrated copper sulfate (CuSO4+5(H2O)) and is water soluble. It is often deposited on the walls of copper mines by seeping water. Crystals are easily created in the lab and often sold as specimens, some of them quite spectacular.
Natural specimens are often ruined when placed in high humidity environments.
Use caution when handling this mineral as it is poisonous.

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Mammoth Tusk
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Photo by Terry Dolph
Courtesy of the San Joaquin Valley Paleontology Foundation

This Columbian Mammoth tusk is about 3 feet long and is 500,000 years old. Their tusks grew to an average of about 6 feet, although some were much longer. The Mammoth stood about 15 feet tall.
The Columbian Mammoth covered most of North America and became extinct about 10,000 years ago.


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Benitoite
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Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Benitoite (BaTiSi3O9) in Natrolite (white) along with Neptunite (dark). This very rare crystal comes from San Benito County, California, and is its state gemstone.

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Horse Skull
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Photo by Terry Dolph
Courtesy of the San Joaquin Valley Paleontology Foundation

This horse fossil is 500,000 years old, and measures about a meter long. The American horse populated Asia and then died out on this continent. They were re-introduced to the Americas by the Spanish Conquistadors.

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Chrysocolla
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 Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Chrysocolla (CuSiO3+2H2O) is a hydrous copper silicate found in the upper, oxidized portions of most copper veins, and is a minor ore of copper.
It is fairly soft, but sometimes used for ornamentation and even jewelry. Because of its color, it is often confused with Turquoise.
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Cassiterite
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Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.

Cassiterite (SnO2) (dark crystal), on white Muscovite, is a major ore of tin, and sometimes used as a gemstone. One of the major uses has been in plating steel to make tin cans.
The color is generally black or brownish, but sometimes red, yellow, or even white.

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Mammoth molar

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Photo by Terry Dolph
Courtesy of the San Joaquin Valley Paleontology Foundation

This molar is from a Columbian Mammoth that lived in California's Central Valley about 700,000 years ago.
These mammoths roamed across most of North America, and went extinct around 8 to 12 thousand years ago.

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Herkimer Diamond
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Photo by Jim Bryan
From the private collection of Mike & Chris Whittier of Rocks in a Hard Place.
Herkimer Diamonds are actually Quartz crystals that come from the area around Herkimer Co., New York. The name is often used, generically, to describe Quartz crystals that are very clear or double-terminated.
They are found in pockets, or vugs, in the surrounding sedimentary rock, or weathered out into stream beds.

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