Neighborhood Rocks                                     Search this Site


Sometimes we find coal in the soil near our home, along railroad tracks, or along beaches.  

Coal formed millions of years ago, when thick layers of dead plants were buried deep within the Earth.

To learn more about coal, scroll farther down this page.

We found these broken pieces of coal in the soil around our home.
These rounded lumps of coal washed up on a Lake Michigan beach.
bulletHow to recognize coal
bulletOther rocks that look like coal
bulletWhere coal came from
bulletHow coal formed
bulletOther names for coal
bulletLinks to Web sites about coal

How to recognize coal

bulletCoal is mostly black in color.
bulletCoal draws a black line if you scrape it on the sidewalk.
bulletMost coal is pretty easy to break into a mix of blocky, crumbly, and powdery pieces that leave your hands dirty.
bulletYou can scratch coal with a nail or knife -- it makes a black powder.  (See more about the scratch test.)

Other rocks that look like coal

Obsidian, also called Volcanic Glass:  
bulletObsidian looks glassy.  (Some coal also looks glassy, but the glassy parts are often mixed with dull crumbly layers.)
bulletWhen you scrape obsidian on the sidewalk, it draws no line or a white line.  (Coal draws a black line.)
Black Shale:
bulletShale breaks into thin, flat pieces.  (Most coal breaks into block chunks or crumbles into bits.)
bulletShale always looks dull.  (Lots of coal has shiny layers or bands.)


Where coal came from

The coal that we find in soil near our home
probably was mined here in Illinois or nearby 
Midwestern states.  It was brought to our 
neighborhood about 50 to 100 years ago, 
when most people had coal-burning furnaces 
to heat their homes.

The coal that we find along railroad tracks and
beaches may have been brought here by trains 
or boats from the either the Midwestern or 
Western United States.


How coal formed

Coal formed from thick layers of dead plants
that piled up in ancient swamps.  The dead-plant
layers were buried deeper and deeper under 
even thicker layers of sand and mud.  During
burial, pressure and heat changed the plant
material into coal.

All this took place millions of years ago.  Coal
from the Western United States usually formed
during or after dinosaur times (about 50 to 100 
million years ago).  Coal from Illinois and nearby
states formed long before dinosaur times (about
300 million years ago).


Other names for coal

Coal is also known by other names:

bulletMost of the coal that we find around here is bituminous coal (also called soft coal).
bulletSometimes we find pieces of anthracite (also called hard coal).  This type of coal was once soft coal, but then it exposed to huge amounts of heat and pressure which made it harder and less crumbly.


Here are some ways to classify coal (by grouping it with similar types of rocks):
bulletBituminous coal is a sedimentary rock.
bulletBituminous coal is sometimes classified as a organic sedimentary rock, because it is made out of the remains of once-living things.
bulletAnthracite is a metamorphic rock.


Links to Web sites about coal

There is a huge amount of information about coal on the Web!
However, most of it is written for adults.  Many of the sites that have 
been developed for children have been created by the coal industry.
Some of these sites seem to advocate for the use of coal in ways
that some environmentalists might not support.  So, surf for coal with 
an open-but-wary mind!

Here's a long Encarta® Concise Encyclopedia article about coal:
   < >

Coal Country is an multimedia introduction to coal and its uses,
suitable for elementary school students.  You can access both
the online preview and the downloadable version here:
   < >

The Life, Death and Afterlife of a Carboniferous Coal Forest is an
illustrated introduction to how coal forms.  This seems most appropriate 
for older students and adults.
   < >

Here's an Encarta® Concise Encyclopedia article about coal mining:
   < > has some articles about coal:
   < >

The American Coal Foundation is an educational group funded by 
the coal industry.  Here's a link to their FAQ and Coal Quiz pages:
   < >
   They also have a section of coal-related educational activities:
   < >

The Coal Education Website is funded by the Kentucky Coal Council.
They have online videos, online mining picture puzzles, and a section 
for teachers.
   < >


Coal is an incredibly complex material.  If you want to learn about
how scientists study coal, you can visit this Web site:

   Petrographic Atlas of Coal and Carbon Compounds
   < >









Copyright 2001-2002 Eric D. Gyllenhaal                                         Search this Site

Neighborhood Rocks is part of the Salt the Sandbox Web. 
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This page was created on October 9, 2001, and it was last updated on July 27, 2002.