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Gemstones 250x250

The Mineral graphite

Flaky Graphite Crystal on Matrix

Graphite is a mineral composed exclusively of the element carbon. Graphite has the same chemical composition as Diamond, which is also pure carbon, but the molecular structure of Graphite and Diamond is entirely different. This causes almost opposite characteristics in their physical properties.


Graphite is rather common mineral, but fine crystals are rare. Most Graphite mining areas produce enormous quantities from a single or several large Graphite veins, but collector specimens in good crystals are not commonly encountered.

Much care should be given to Graphite specimens, especially thin crystals, which are fragile. It may be difficult to wash crystals, as they easily peel off and get ruined. Graphite will also smudge on its surface, and can get worn out if it is moved around too much. It also smudges the hand when handled, and will smudge a label or cardboard box if stored in one.

Chemical Formula

C

Color

Silver-gray to black

Crystal System

Hexagonal

Properties

Streak
Black
Hardness
1 - 2
Transparency
Opaque
Specific Gravity
1.9 - 2.3
Luster
Metallic
Cleavage
1,1 - basal
Fracture
Conchoidal
Tenacity
Brittle; thin flakes are flexible
Other ID Marks
1) Has a greasy feel.
2) Smudges the hands when touched.
3) Good conductor of electricity (though a poor conductor of heat).

Crystal Habits

Crystals consist of thin hexagonal plates or distorted clusters of flaky plates on a matrix. Large thick hexagonal crystals are rare. Most often occurs as veins, as foliated masses, and in massive form. Small, rounded ball-like aggregates and radiating spheres also occur, as do rounded, waterworn pebbles.

3D Crystal Atlas

Additional Information

Composition
Carbon
In Group
Native Elements; Non-Metallic Elements
Striking Features
Low weight, greasy feel, smudge, and low hardness.
Environment
Most often in metamorphic rock caused from the metamorphism of carbonates. Rarely in pegmatites and hydrothermal veins.
Rock Type
Igneous, Metamorphic

Varieties

 -   Rare hexagonal polymorph of Graphite and Diamond formed only in a meteoric environment where extreme heat and pressure caused it to form. To date, it is only found in Mottigen, Ries Crater, in Bavaria, Germany. As it differs in crystal structure, Chaoite is scientifically categorized as an individual mineral species.

Uses

Much of the commercially mined Graphite is used for pencil fillings. The "lead" filling in pencils is in fact composed of a mixture of Graphite and clay. Graphite's main function, however, is as a lubricant. It has many electrical uses, primarily because it is the only common nonmetal that is a good conductor of electricity.

Noteworthy Localities

Although Graphite is not particularly rare, good Graphite crystals are uncommon. Well-known worldwide localities for Graphite are Pargas, Finland; Mount Vesuvius, Italy; Borrowdale, Cumbria, England; and Mont Saint-Sauveur, Quebec, Canada. The Merelani Hills of Arusha, Tanzania, has produced sharp crystal plates that are associated with Diopside and Garnet.

In the U.S., extensive commercial Graphite deposits exist in Ticonderoga, Essex Co., New York, and in Clay Co., Alabama. Graphite as small flakes and plates is common in the Franklin Marble Belt, specifically at Amity, Orange Co., New York, and across the state border at Franklin, Ogdensburg, and Sparta, Sussex Co., New Jersey. Crystal masses and large plates have also come from the Hudson Highlands region, especially near Stony Point, Rockland County, New York. A new, significant find of this mineral is Rossie, St. Lawrence Co., New York. Graphite crystal flecks have been found at the French Creek mine Chester Co., Pennsylvania; at Bisbee, Cochise Co., Arizona; and at Crestmore, Riverside Co., California.

Common Mineral Associations

Calcite, Quartz, Muscovite, Biotite, Hornblende

Distingushing Similar Minerals

There are quite a number of minerals similar in appearance to Graphite, but Graphite's intrinsic properties will easily distinguish it. Molybdenite, which is commonly confused with Graphite, is heavier and does not smudge.


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