FROM MINERAL TO ROCK
Minerals are made of atoms (tiny particles) from
different elements such as oxygen, carbon, lead and
silicon. The atoms form simple patterns that give
mineral cystals characteristic shapes. The hidden
pattern of the packed together atoms is always the same
in any particular mineral. Minerals can be identified by
their color, density, hardness and shape.
Color: Streak is a mineral's color in powder form. It
can be seen when the mineral is scraped across a
tile.
Density: This is the mineral's weight per unit
volume. Water is assigned a density of 1 and the
specific density measurements of other materials are
compared to it. A mineral fragment that weighs 2.1
times as much as an equal volume of water has a
density measurement of 2.1.
Hardness: A mineral's hardness is one of the most
useful identification tools. The hardness scale looks
like this:
Shape: A mineral's shape (also called “habit”) can
be a useful clue to a mineral's identity. Each shape
has a specific name. For example, copper is
dendritic. It is made up of thousands of tiny crystals
forming a branching growth. Salt forms cube-
shaped crystals and quartz forms six-sided crystals.
Cleavage: This is the surface along which a mineral
has the tendancy to break. The number of cleavage
planes and the angles between them can provide
useful clues to identification of minerals.
Luster: Luster is the gloss of a mineral's surface. It
is determined by the way light is reflected from a
mineral.
MINERALS ALL AROUND US
Minerals are all around us. They are used to make
many of the products we use everyday. Minerals
provide us with the metals that help us make cars,
aircraft, jewelry and coins. Below is a list of other items
we use that are made of minerals:
lead pencils (graphite)
fertilizer (potassium, sodium, calcium)
chalk (gypsum)
flashbulb (zirconium)
window glass/mirrors (silica)
table salt (halite)
Minerals that concentrate into deposits from which one
or more minerals and rocks may be extracted are called
ores. In Michigan, iron ore (hematite) is mined in the
Upper Peninsula. The earliest commercial deposits
were found in Marquette County in 1844. Until about
1900, Michigan was the leading producer of iron ore in
the United States.
Another mineral that brought attention to Michigan was
the “native copper” deposits of the Keweenaw Peninsula
in the western Upper Peninsula. This region became
world famous when Michigan was the leading producer
of copper in the U.S. between 1847-1887. This deposit
is unique because the copper is not combined with other
elements.
THE BUILDING BLOCKS OF ROCK
Minerals are the building blocks of rocks. Nature
cements combinations of minerals together to form
rocks. Rocks are catagorized in three general groups
according to the way they were formed. These groups
are:
IGNEOUS ROCKS: Igneous rocks are not all one kind,
so they are put into two sub-groups according to the
manner and place in the earth where they were formed.
Intrusive igneous rocks were formed by molten
rock, called magma, forced from the earth's interior
into a cooling part of the earth's crust. As they
cooled, their minerals formed large crystals. To
summarize, intrusive rocks are those that were
pushed into other rocks.
Extrusive igneous rocks are formed when magma
is forced to the earth's surface as a result of volcanic
activity.
From Mineral to Rock – Page 1 of 2
