h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The first sentence is grammatically incorrect. It reads, "You all know what a rocks is." This should either be "You all know what a rock is" or "You all know what a rocks are."

Also, quartz is misspelled as quatrz in the list of igneous rocks.

Doh! Ahem. "You all know what rocks are" is surely what I meant.

*sheepish grin*

Thanks for this.

Should be all better now

It's peachy. Thanks!

Always a pleasure...

Also, shouldn't it be "petroglyphs" in the sentence:
"Newspaper Rock, Moab, Utah, USA is a sandstone cliff on which is inscribed hundreds of native American pertoglyphs (carved images) in the stone."

Yep. I missed that one.

And let's point out that coal is a metamorphic rock as it is plant material that transforms into coal over time when given the proper pressure and heat. Sedimentary rocks are things that are laid down by the action of water.

Sorry, the same goes for diamonds as igneous and oil strata as sedimentary - both are metamorphic.

Coal comes in several grades: it can be unlithified sediment, lithified sediment (sedimentary rock) or metamorphosed sedimentary rock (like anthracite coal from Wyoming). Sedimentary rocks are NOT just laid down by water!

Quartzite is not an igneous rock--it is a metamorphosed sedimentary rock. Most of the landmark theories about metamorphism came from research done in the Baraboo Hills in central Wisconsin: the rocks there are mainly quartzite and scientists like Van Hise proposed some fundamental theories after comparing bedded sequences of metamorphosed sandstone (quartzite) and metamorphosed shale.

Quartz is a mineral which is commonly found in igneous rocks--it is definitely not "a rock" in geologic terms.

The definition of sedimentary rock is very limited. In fact, two of the rocks (gypsum and limestone) don't even fit the description since they form in evaporite basins or from fossil deposition in ocean basins.

Metamorphic rocks could definitely use some examples: marble is a good one, since many people have seen it. Slate is great, too: everyone knows what a blackboard is like.

Under igneous rocks, the example of "lava rocks" is pretty vague. Is this basalt? Rhyolite?