|How do heat,time, and pressure contribute to
The type of minerals that form depend first on the
basic chemical material that is available. For
instance, it you have lots of iron and sulfur
around, you would get different minerals than if
you have mostly silicon and oxygen available.
Temperature and pressure also make a big
difference in mineral formation. The basic
chemical materials may be the same, but as the
pressure and temperature change, the actual
minerals will change too.
Think of it like
stacking wooden blocks -- you can stack the blocks
so they have gaps between them or you can stack
them so the blocks are extremely close together
and touching. It is the same with minerals, the
same basic chemical materials can be stacked in
several different ways and you get several
different minerals. How tightly the mineral
structure is packed depends on the temperature and
pressure.Time will determine the size the crystals
reach. If magma cools to rock slowly, the
crystals will be larger. If the magma cools
slowly, many tiny crystals will form.
Matter is stable in different states at different
temperatures and pressures. Consider water, for
example: at sea level, water is most stable in
solid (ice) form below 0 C, and most stable in
vapor form above 100 C, and can exist either as a
vapor or as a liquid in-between. As you go up in
the mountains, the pressure drops, and so does the
boiling point, the point where liquid is no longer
stable. Now, there are multiple phases of ice as
well, different orientations of atoms within the
The same is true of all substances,
although of course the numbers are different.
Time, however, is required for the phase to change
and for crystals to grow. Just getting water to
the boiling point, as you know, does not cause it
to all turn instantly into steam - it can take a
while for it to boil away. Water tends to
crystallize, melt, and otherwise change phase much
more rapidly than many other substances - minerals
take tremendous periods of time to change and
grow. Diamond, for instance, is not stable at the
surface of the Earth, but it takes eons for it to
turn into graphite at surface pressure. If you
heat it up, however, it will turn into graphite
Mineral formation, as you've already probably
hypothesized, is a process involving the variables
you've mentioned: heat, time and pressure. For
minerals to form, they also need the raw materials
that make up the finished mineral. All four of
these are necessary to form minerals. The time
that a mineral has to grow generally just
determines its size. The longer it grows, the
larger it will be.
Heat and pressure
determine what type of mineral forms. Some
minerals need very little heat and pressure to
form (like quartz), and actually break up or melt
if heated up or put under large amounts of
pressure. Other types of minerals (metamorphic)
need a lot of heat and pressure to form; at low
temperatures the mineral's raw materials can stay
mixed up with other minerals' raw materials.
There are many types of minerals and places in the
earth's crust where they can form. If you're
interested you could look up hydrothermal
deposits, magmatic minerals and metamorphic
minerals to find out more.
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