How to identify it
Unique Characteristics or Properties
Tuff can be amazingly variable, as it is formed from whatever is falling from a volcano. It often can be banded, as larger ash falls first and then smaller falls later. It can range in size from very fine grained to large boulders in it. The example picture here is of a larger grained variety, but is still tuff as it came from volcanic fallout reforming into new rock.
Where to find it in
The Northwest: Much of Washington and Oregon, thanks to the Mount St. Helens explosion.
Other: New Zealand, Easter Island, Greece, Peru.
How it was Made
Tuff is made from particles that were expelled from a volcano. Those can be from a pyroclastic flow, ash falling, or almost any other small particles. As they settle together they are either fused right away if it’s hot enough, or over time like other sedimentary rocks.
The famous statues on Easter Island are made from tuff. When it forms from a hot ash flow it can create shells around objects, even people. This happened at Mt. Vesuvius and preserved the shapes and postures of the people that were trapped by the eruption and covered by ash.
More Information on the Web: Mt. Vesuvius Info Wikipedia:Mt. St. Helens