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Rocks and Minerals: Glossary

B

bed
a layer of sediment or sedimentary rock
boulder
a loose rock larger than 256 millimeters (10 inches)

C

cobble
loose particles of rock or mineral that are the size of gravel larger than pebbles, but smaller than boulders
conglomerate
sedimentary rock made of rounded pebbles held in together with a matrix
core
the huge mass in the very center of the Earth made mostly of iron and nickel. It is divided into an outer core and inner core
crust
the solid outermost part of the Earth. The crust is all the land you see and the land on the ocean bottom
crystal
a solid in which the particles are arranged in a pattern to make shapes with flat surfaces

E

earthquake
sudden release of energy built up in an area on the crust or upper mantle sudden ground motion or vibration of the Earth
element
substances which cannot be broken down into other substances
erosion
the movement of weathered rocks and soil

F

formation
a body of rock with special that allow geologists to map, describe, and name it
fossil
something that has lasted from a living thing that died long ago. They can be body parts, that have turned into stone or animal tracks

G

geologist
a scientist who studies geology
geology
the science of the rocks and minerals that compose the earth, of its structure, and of its history
gravel
all sedimentary particles larger than 2 millimeters is called gravel. Gravel is subdivided into pebbles, cobbles, and boulders

I

igneous rock
rock formed when molten rock has cooled and solidified
intrusive rock
igneous rock that forms when magma cools below the Earth's surface

L

lava
molten rock that flows out onto the Earth's surface

M

magma
molten rock that is located beneath the Earth's surface
mantle
the thick layer of very hot, melted rock between the crust and the core of the Earth
matrix
fine-grained material surrounding larger grains in a sedimentary rock
metamorphic rock
rocks that are changed from sedimentary, igneous or other metamorphic rocks by intense pressure and heat
mineral
a non-living, solid material with particles arranged in a repeating pattern called a crystal. A mineral is usually a combination of 2 or more elements. A mineral cannot be broken down into any other substance
mineralogist
a scientist who studies the identification, properties, and distribution of minerals
Moh's scale
a scale used to measure the hardness of a mineral
molten
melted

P

pebbles
Loose particles of rock or mineral that range in size from 2–64 millimeters in diameter. Pebbles are the smallest type of gravel

R

rock
a combination of 2 or more minerals which have been joined either by heat, temperature, pressure, or chemical changes
rock cycle
the process in which igneous, sedimentary, and metamorphic rocks are changed over time

S

sand
loose particles of rock or mineral that range in size from 0.0625–2.0 millimeters in diameter
sediment
material that comes from the weathering of rock or from from fragments of plants and animals that settles to the bottom of rivers, lakes, and seas
sedimentary rock
rock formed from rock types that have weathered, cemented, and/or squeezed together
sedimentation
the process of breaking up rocks into smaller fine pieces that sink to the bottom of rivers, lakes, and seas
shale
soft rock formed from layers of mud soil; very small weathered fragments of rock mixed with decaying plant or animal material
strata
layers, or bands, in rocks

V

volcanic
igneous rock that forms when magma cools on the Earth's surface

W

weathering
the breaking of rocks by water, snow, ice, wind, chemicals, gravity or plant roots
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