Iron Pyrite-Deposits of Fool’s Gold
Iron pyrite has long been given the nickname “Fool’s Gold”. Iron
pyrite or simply pyrite, is composed of iron disulfide (FeS2). That
means for every one atom of iron (Fe) there are two sulfur (S2)
atoms, the three atoms are bonded together to make one molecule of
iron pyrite. Most people are familiar with the chemical formula for
water, H2O, which of course means two atoms of hydrogen (H2) and
one atom of oxygen (O) are bound together to make one molecule of
water, these are of course way too small to see with the naked
eye.
The picture above shows a small portion of the deposit of iron
pyrite found at this location. It is scattered along the bank and
can be found a little higher up as a thin, intermittent layer.
Small fragments can be seen from the original layer down to the
ditch line.
Pyrite gets its name from the Greek word for fire, “pyros”
because when struck it may produce sparks. It is much harder than
real gold, therefore a wise (non-fool) person would easily be able
to tell the difference. Also, it may have an odor like rotten eggs,
that’s the sulfur supplying that quality. It has a metallic luster
and a gold-brassy appearance, when not oxidized. When it tarnishes
it appears to be greenish-black to brown.
Pyrite forms in organic-rich marine environments and if you look
at the rock in this location you may see a few fossils. These
living organisms provided the organic-rich part of the environment
needed for this substance to form. Bacteria caused the bodies of
these animals to decay when they died, releasing carbon, sulfur and
other elements. This allowed the process to begin for the formation
of the pyrite. The reaction of the sulfur with dissolved iron
produces iron sulfides, the most common of which is pyrite. It may
form as a cube with six sides, or twelve or a five sided geometric
shape.
Iron pyrite can sometimes be found in fossils and I have even
seen it on the surface of nickel-iron meteorites that fell to the
earth thousands of years ago. But once exposed to moisture, rain or
just humid air it starts to oxidize (rust is a form of oxidation).
The photo above shows iron pyrite being oxidized. If you scrape or
polish the surface of these tiny pieces you can see the gold color
of the pyrite without the oxidized surface.
Marcasite is another form of iron pyrite and is easily mistaken
for fool’s gold. It has the same basic chemical formula (FeS2), but
just as coal and diamonds are two forms of carbon, so is marcasite
and iron pyrite. Marcasite takes different shapes as it is forming
and may be a yellowish-green as it oxidizes to a powder. They have
the same hardness (6-6.5 on the Moh’s scale) but pyrite has a
somewhat higher specific gravity (the ratio of its weight compared
to that of water), around 5.1 compared to 4.8 for marcasite.
Qualifications for credit:
To get credit for the earthcache, email the answers to the
following questions and then post a CLOSE-UP picture (or a picture
of you and your GPSr , similar first picture above) of your GPSr
and a piece of the iron pyrite when you log your find. Posts with
no pictures or without emailing the answers will be deleted. If no
picture is possible, for instance you dropped your camera in the
ditch and it broke or the batteries died, let us know first and we
will work something out.
Questions:
1. What is the elevation at this site?
2. Where did the name for pyrite come from?
3. How can you easily tell the difference between iron pyrite
and real gold?
Credits and Ammosuperman EarthCaches:
This EarthCache was created by a team of two Platinum EarthCache
Masters, Ammosuperman EarthCaches are a collaborative effort. We
have used resources such as the Internet and magazine articles as
well as personal experience in visiting the sites, as research
tools in its construction. Our goal is to learn more about our
planet and to pass along what we have learned to others having
similar interests. We hope you enjoy the experience.
