How Diamonds Form (Chapter 4, Key Terms & Key Concepts) Flashcards
Earth’s innermost layer
Core
Ancient, large, and
stable parts of the earth’s
continental crust
Cratons
The surface and outermost
layer of the earth.
Crust
A geologic
process that delivers materials
(sometimes diamonds) to the
surface
Emplacement
A category of
rocks formed from a molten state.
Igneous rock
An igneous rock
that transports diamonds to the
surface.
Kimberlite
An igneous rock, rarer
than kimberlite, that transports
diamonds to the surface.
Lamproite
Layer between the
earth’s crust and its core.
Mantle
A category of
rocks that have been altered by
heat and pressure.
Metamorphic rock
A deep vertical formation at
the earth’s surface that results
from a kimberlite or lamproite
emplacement
Pipe
Process in which two
crustal plates collide, forcing one
under the other
Subduction
Diamond and graphite are both made
of carbon.
Key Concept
Diamonds form in cratons, which are
located only under continental landmasses
Key Concept
The carbon needed for diamond
formation is always present.
Key Concept
Diamonds might wait hundreds of
millions of years before they’re carried
to the surface.
Key Concept
Diamonds that exist today were
delivered to the surface between 2.5
billion and 20 million years ago.
Key Concept
Kimberlites and lamproites transport
diamonds to the surface (through the pipe), but diamonds
don’t form in them.
Key Concept
Very few kimberlites actually contain diamonds.
Key Concept
During emplacement, if diamonds are exposed to high temperature along with decreased pressure for a long period, they will
convert to graphite.
Diamond and graphite are both made of
carbon.
How far beneath the earth’s surface do diamonds form?
90 to 140 miles (140 to 220 kilometers)
The proper environment for diamond formation includes the right temperature, pressure and
the availability of carbon.
Before arriving at the earth’s surface, diamonds might remain in the mantle for as long as a few
hundred million years.
Diamond is hard and graphite is soft because of the difference in
the way their atoms fit together.
Subduction occurs when
two of the earth’s crustal plates collide.
Most of the world’s kimberlite pipes
do not contain diamonds in profitable quantities.
The three main components of the earth are the crust, mantle, and
core.
The deep vertical formations through which diamonds traveled to the surface are called
pipes.
The first authenticated diamond discovered in South Africa is named the
Eureka.
Scientists have found that diamonds form in two types of rocks, called
peridotite (igneous rock) and eclogite (metamorphic rock).
The correct conditions for diamond formation exist under
cratons.
The large, stable parts of the earth’s continental crust are called
cratons.
Diamonds were delivered to the earth’s surface as recently as
20 million years ago
