I've also used the soda can, toilet paper roll, apple, once and acorn cap for hash in the Marines. :S2:

And to show I'm not crazy about the billion year thing.

In a nutshell, the Early Proterozoic Sioux Quartzite of southwestern Minnesota accumulated as sedimentary sand layers deposited by streams that flowed across an erosional surface developed on older Archean rocks. These deposits were metamorphosed by heat and pressure to produce the metamorphic layers of quartzite seen today. The thin 2 to 6 inch layers of reddish-brown catlinite - a metamorphic claystone argillite - is normally found sandwiched between layers of quartzite which is often found under an overburden of 10-15 feet. The catlinite deposits of southwestern Minnesota are estimated to be between 1.6 billion and 1.8 billion years old.
For more information about geologic time, visit our Geologic Time Page.

The specimen above is a great example, on a small scale, of how the deposits appear.

Catlinite is a mineral made up of diaspore, pyrophyllite, muscovite and hematite, along with traces of anatase and chlorite. Catlinite gets it rusty, reddish color from oxidized hematite - an ore of iron. It is composed of: silica (49.01 percent), alumina (35.17 percent), magnesium (0.23 percent), water (5.87 percent), potash (5.62 percent), ferric acid (3.06 percent) and titanium dioxide (0.44 percent).
Catlinite is very soft measuring 2.5 on Mohs Scale of Hardness. That is about the same hardness as a human fingernail and provides the unique sofness necessary for shaping it into pipes and other objects. For more about Mohs scale, go to our Mohs Scale page.

The specimen above is a great example, on a small scale, of how the deposits appear.

Minnesota Pipestone (Catlinite) from Rockman