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Scoria (a type of Basalt) 

Basalt is a dark-colored rock that formed as lava cooled and hardened.  Scoria is a type of basalt that's full of bubble holes.  The bubbles formed as the lava was blasted out of a volcano, and were trapped as the lava cooled and hardened. 

The scoria in our Chicago-area neighborhood came all the way from Idaho. 

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

Black-colored scoria
Red-colored scoria
bulletHow to recognize scoria
bulletOther rocks that look like scoria
bulletSpecial things to look for
bulletWhere scoria came from
bulletHow scoria formed
bulletOther names for scoria
bulletLinks to Web sites about scoria, lava, and volcanoes

How to recognize scoria

bulletScoria can be black, dark gray, or red.
bulletScoria is full of holes, and the holes are often uniform in size and shape.
bulletDespite all the holes, scoria doesn't float in water.

Other rocks that look like scoria

bulletCompared with natural scoria, slag is often more glassy looking, and there are lots of different colors on some pieces.
bulletThe bubble holes in slag are less regular in size and shape.
bulletPumice is usually tan or light gray, and is often more glassy looking than scoria.
bulletDry pumice feels very light weight for a rock -- it often floats in water.
bulletPumice often looks more delicate than scoria, because the bubbles holes are often smaller and the rock walls between the holes are thinner and more transparent.

Special things to look for

Some bags of scoria include more solid chunks of basalt.
Look really close, and you may see bubble holes with interesting shapes.  Some of these holes looks like they were stretched out before they hardened.

Where scoria came from

The scoria in our Chicago-area neighborhood 
came all the way from Idaho.  

We're wondering if our scoria was quarried 
from relatively young volcanoes, like the ones 
that made Craters of the Moon National Monument,
or more ancient lava flows, like the Columbia 
River flood basalts
.  We'll update this Web page
once we find out.


How scoria formed

Scoria formed as lava exploded out of a volcano. 
Gas bubbles formed inside the lava, and were 
trapped as the lava cooled and hardened into rock.


Other names for scoria

We use the scientific name "scoria" for this rock,
but it is also known by other names:

bulletWe've seen 50-pound bags of scoria gravel labeled "volcanic rock" and "crater rock." 
bulletSome people in our neighborhood call it "lava rock."
Here are some ways to classify scoria (by grouping it with similar types of rocks):
bulletScoria is a variety of basalt.
bulletScoria is an igneous rock, because it formed from melted rock.
bulletScoria is an extrusive igneous rock, because it formed from lava "extruded" onto the surface of the Earth.


Links to Web sites about scoria, lava, and volcanoes

Here's a Franklin Institute Web page about scoria.  Be sure to 
follow the "See how igneous rocks are formed" link at the 
bottom of the page:
   < >

Here's a United States Geological Survey article about 
   < >

The VolcanoWorld Website has a good article about 
Craters of the Moon National Park in Idaho (written for 
older kids and adults.)  It includes pictures of basalt lava 
< >

VolcanoWorld also has a good article about the Snake 
River Plain and Columbia River flood basalts in Idaho 
and nearby states:
< >

VolcanoWorld has lots of information and activities for kids:
   < >








Copyright 2001-2002 Eric D. Gyllenhaal                                         Search this Site

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This page was created on May 2, 2001, and it was last updated on July 27, 2002.