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Rocks and Minerals

Rocks and Mineral Samples

Rock and mineral specimens from my collection. Some of the pieces were purchased from dealers.


Aquamarine Mineral Sample

Beryl (Aquamarine)

Chemical formula Beryllium aluminum silicate (Be3Al2Si6O18)
Mohs Hardness 7.5-8.0
Specific Gravity 2.72
Luster Vitreous - Resinous
Cleavage Imperfect
Streak White
Crystal Hexagonal
Fracture Brittle. Produces small, conchoidal fragments.

Aquamarine is a blue variety of beryl. Other beryl varieties include morganite (pink), heliodor (greenish yellow), bixbite (red), emerald (green), and goshenite (colerless).

I found these specimens at the Brushy Creek Aquamarine Mine near Spruce Pines, North Carolina in May, 2009


Schorl Tourmaline Mineral Sample

Tourmaline (Schorl)

Mohs Hardness 7.0-7.5
Specific Gravity 3.06
Luster Vitreous
Cleavage None
Streak White
Crystal Hexagonal, with a rounded triangular cross section. Lengthwise striations.
Fracture Brittle. Produces small, conchoidal fragments.

Schorl is a variety of tourmaline. Other varieties include elbaite, indicolite, rubellite, and dravite.

I found these specimens at the Brushy Creek Aquamarine Mine near Spruce Pines, North Carolina in May, 2009


Corundum Mineral Sample

Corundum Mineral Sample

Corundum (Sapphire and Ruby)

Chemical formula Aluminium oxide (Al2O3)
Mohs Hardness 9.0
Specific Gravity 3.95-4.10

Composed of Aluminum oxide, sapphires come in a variety of colors and are some of the hardest natural substances. Red sapphires are known as rubies.

Varieties of corundum are valued as gemstones and for use as abrasives.

I found these samples near Franklin, North Carolina in May, 2009


Garnet Mineral Sample

Garnet

Mohs Hardness 6.5 - 7.5
Specific Gravity 3.5 - 4.3

Some varieties of garnet are valued as gemstones and for use as abrasives.

I found these specimens in 2009 at the Brushy Creek Aquamarine Mine, located near Spruce Pine, NC.


Epidote Mineral Sample

Epidote

Mohs Hardness 6-7
Specific Gravity 3.3-3.5

These pieces were found at the Caledonia Mine near Mass city, Michigan.


Calcite Mineral Sample

Calcite

Chemical formula Calcium carbonate (CaCO3)
Mohs Hardness 3
Specific Gravity 2.71

This specimen was found at the Caledonia Mine near Mass city, Michigan.


Sample of Optical Calcite

Calcite (Optical)



Photo of a Gypsum Desert Rose

Gypsum

Chemical formula Hydrated calcium sulfate (CaSO4*2H2O)
Mohs Hardness 1.5-2
Specific Gravity 2.35


Feldspar Mineral Sample

Feldspar


I found this specimen in 2009 at the Brushy Creek Aquamarine Mine, located near Spruce Pine, NC.


Mica Sheet specimen

Mica Sheet

This sample measures 15cm wide and around 4cm thick.

I found this specimen in 2009 at the Brushy Creek Aquamarine Mine, located near Spruce Pine, NC.


Copper specimen

Copper

Chemical formula Copper (Cu)
Mohs Hardness 2.5-3
Specific Gravity 3.93

These pieces were found at the Caledonia Mine near Mass city, Michigan.


Pyrite specimen rock

Pyrite

Chemical formula Iron Sulfide (FeS2)
Mohs Hardness 6-6.5
Specific Gravity 5.0-5.2
Luster Metallic

Pyrite is sometimes called 'Fools Gold' because of its appearance.


Tourmaline and Feldspar specimen rock

Tourmaline, Feldspar and Quartz


I found this specimen in 2009 at the Brushy Creek Aquamarine Mine, located near Spruce Pine, NC.

Quartz Samples


Specimen of the mineral Quartz

Quartz

Chemical formula Silicon dioxide (SiO2)
Mohs Hardness 7.0
Specific Gravity 2.65


SmokeyQuartz Mineral Sample

Smokey Quartz


Rose Quartz Mineral Sample

Rose Quartz


Amethyst Quartz Mineral Sample

Amethyst Quartz

Rock and Mineral Definitions

Cleavage The tendency of some minerals to break along certain planes.
Crystal Habit The shape in which individual crystals grow and the manner in which crystals grow together in aggregates.
Fracture The way in which a mineral breaks other than along planes of cleavage.
Hardness The resistance of a minerals surface to scratching. Can be evaluated using the Mohs scale of hardness (see right column).
Lava Magma flowing out of a volcano.
Luster The manner in which a mineral reflects light.
Magma Molten rock. Temperatures in the range of 700*c to 1300*c. Consists of silicon, oxygen and other minerals.
Mineral A naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure.
opaque A material that blocks the passage of light.
Polymers Very large molecules.
Silicates Minerals that contain both Si and O.
Specific Gravity The weight of a substance relative to the weight of an equal volume of water.
Streak The color of a fine powder of a mineral. Scratch a mineral sample on a streak plate to make streak.
Translucent A material that permits the passage of light.
Twinning Two or more crystals that have grown together in a symmetrical manor.
Viscosity Resistance to flow.

T-Shirts and Other Gifts for Rockhounds

Just a few of the natural science gifts available at History and Science T-shirts and Gifts.



T-rex dinosaur T-shirt

Tyrannosaurus rex Skull T-Shirt

Photograph of a T-rex skull. Great gift idea for anyone interested in dinosaurs! This design is available on mugs, t-shirts and more. Other skull designs include Triceratops, Hadrosaur, Gorilla, and Human versions.

Beware of the Rockhound T-shirt

Beware of The Rockhound T-Shirt

Humorous design includes the words 'Beware of The Rockhound' and 'Owner assumes no responsibility.' A great gift idea for any Rockhound! This design looks great on posters, cards and t-shirts.

Do not feed the Rockhound T-shirt

Please, Do Not Feed The Rockhound T-Shirt

Humorous design includes the words 'NOTICE - For your own safety! - Please, Do Not Feed The Rockhound!' This popular design is also available for 'Paleontologist' and 'Geologist'.

Arrowhead Wall Clock for sale

Arrowhead Wall Clock

Unique wall clock featuring a Native American arrowhead! This artifact was found in Chelsea, Michigan. Great gift idea for anyone interested in American Indian Culture!

Wall Clock with T-rex image

Tyrannosaurus Wall Clock

Wall clock design featuring an image of a Tyrannosaurus rex skull. Great gift idea for anyone interested in dinosaurs!

There are over 30 science and history themed wall clock designs at Explore Store Gifts. Each clock design is available in three clock styles. Other dinosaur designs include Triceratops and Hadrosaur versions.

Rock Collector T-shirts and Gifts

A variety of rock collector designs available on t-shirts, sweatshirts, hats, and other products. Great gift ideas for rock hounds, geologists, and science buffs.

Gifts for rock and mineral collectors

Find dozens of Earth-science themed gifts at History and Science T-shirts and Gifts.


Mohs Hardness Scale

Developed by Frederich Mohs in 1812, the Mohs hardness scale is used to identify mineral samples. The scale associates a common mineral with a range from one to ten. The Mohs scale is not a linear scale.

The following table lists ten minerals that comprise the Mohs scale. The number in parentheses indicates the relative hardness. For instance, calcite, '3' on the Mohs scale, is actually nine times harder than talc, which is '1' on the scale.

Mineral Hardness
Talc 1 (1)
Gypsum 2 (3)
Calcite 3 (9)
Fluorite 4 (21)
Apatite 5 (48)
Feldspar 6 (72)
Quartz 7 (100)
Topaz 8 (200)
Corundum 9 (400)
Diamond 10 (1600)






Luster

Luster describes a minerals appearance. Specifically, how light reflects from the mineral.

Terms Used to Describe Luster

Adamantine

Transparent to translucent. Very brilliant and shiny. Example: diamond.

Dull

Very low reflectivity. Like unglazed pottery.

Greasy

Appears to be covered with grease.

Metallic

Reflective and opaque. Like metal. Example: pyrite.

Pearly

Similar to the inside of a sea shell.

Pitchy

Similar to tar.

Resinous

Similar to honey. Example: amber.

Silky

Similar to silk cloth.

Submetallic

Reflective and nearly opaque. Splinters may be translucent.

Vitreous

Similar to glass. Example: quartz.

Waxy

Appears to be covered with wax.