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Rock and Mineral Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on an underlined word for more information on that subject.
If the rock or mineral term you are looking for is not in the dictionary, please e-mail us and we'll add it.

Click on an underlined word for more information on that subject.

E



Earth

The Earth is the third planet from the sun.
Soil Layers diagram
E Horizon

This eluviation (leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon. It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil (in the process of eluviation).


Eilat stone

Eilat stone is only found in King Solomon's copper mines on the Red Sea, near Eilat, Israel. This opaque green mineral is composed of azurite, malachite, turquoise, and chrysocolla. The hardness of this copper-based stone varies. There are many variations on its spelling, including Eliat, Elat, and Ellat.

ejecta

Ejecta is material that has been thrown from a volcanic erutption. Some ejecta are lava bombs and tephra (pyroclastic material).

element

An element is a chemically pure substance composed of atoms of a single type.

Elie ruby

An Elie ruby is actually a pyrope garnet (and not a ruby at all).

emerald

Emeralds are a very hard, green precious stone (beryl, Be3Al2Si6O18, colored by chromium and some vanadium impurities). Flaws and cloudiness (called jardin) are very common in emeralds, so many emeralds are oiled, irradiatied,and dyed to improve their look. Synthetic emeralds (developed by Carroll Chatham in the 1930's) have fewer imperfections and are very hard to distinguish from natural emeralds. Emeralds belong the beryl group of stones which also includes aquamarines, morganite, and chrysoberyl). Emeralds have a hardness of 7-8 and a specific gravity of 2.6 - 2.8. Emerald (and all forms of beryl) have large, perfect, six-sided crystals. Emeralds were long thought to have healing powers, especially for eyesight. During the renaissance, emeralds were used as a test for friendship among the aristocracy; an emerald given to a friend would remain perfect as long as the friendsip endured.

enhanced

Enhanced stones are stones that have been treated to improve their color, clarity, finish, strength, or other characteristics. Some common enhancements are heat-treatment, irradiation, coating the surface, filling cracks, oiling, surface diffusion (coating the surface then applying heat), bleaching, dyeing, etc.


Eocene epoch

The Eocene epoch (58-37 million years ago) was the time when primitive whales and many other mammals evolved.
Eon Time
Phanerozoic Eon 540 million years ago through today
Proterozoic Eon 2.5 billion years ago to 540 million years ago
Archaeozoic Eon 3.9 to 2.5 billion years ago
Hadean Eon 4.6 to 3.9 billion years ago

eon

Two or more geological eras form an eon, which is the largest division of geological time, lasting hundreds of millions of years.

epipelagic

Epipelagic menas of or about the upper part of the ocean in which there is enough light to support plants.

epoch

An epoch is a division of a geologic period; it is the smallest division of geologic time, lasting several million years.


equator

The equator is an imaginary circle around the earth (or other planet or moon), halfway between the north and south poles.

era

Two or more geological periods comprise an era, which is hundreds of millions of years in duration.


eruption

An eruption is volcanic activity in which lava, tephra, or gases are released.

eruption cloud

An eruption cloud (also called an ash cloud) is the cloud of ash, gas and rock fragments that forms after some volcanic eruptions.


eruptive vent

An eruptive vent is a vent from which volcanic material is released.


evaporation

Evaporation is the process in which a liquid is transformed into a gaseous form.

EverGreen topaz

EverGreen (R) is a trademarked type of diffusion-treated topaz. This deep green stone is produced by heating a cut, colorless topaz with coloring chemicals (mineral oxides), resulting in a thin layer of green coating the outside of the stone.

Excelsior diamond

The Excelsior is the second- or third largest diamond (depending on whether or not the Braganza diamond was actually a diamond). This irregular-shaped blue-white diamond was roughly 995 carats. It was found in l893 by a worker at the De Beers mine at Jagersfontein, Orange Free State, South Africa. The Excelsior diamond was cut in 1904 by I.J. Asscher and Company of Amsterdam into 21 stones, including a 69.80-carat marquise, an 18-carat marquise stone (which was displayed at the l939 World's Fair by the De Beers company), and many other stones.

extinct

An animal species that is extinct has died out. Most animal species that ever existed have gone extinct, including all the dinosaurs.

extinct volcano

An extinct volcano is a volcano that is not likely to erupt again.

extrusive igneous rock

Extrusive rocks are igneous rocks that have cooled at the surface of the Earth. They usually have a fine-grained texture.

EnchantedLearning.com
Rock and Mineral Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on an underlined word for more information on that subject.
If the rock or mineral term you are looking for is not in the dictionary, please e-mail us and we'll add it.

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