A pocket sized magnifier of any type will be acceptable at the event.

A published or commercially published field guide is any printed resource that is published and used for identifying natural objects, flora, or fauna.

According to the National Audubon Society Field Guide to North American Rocks and Minerals, a recommended resource listed in the SO rules manual, Anthracite Coal is a sedimentary rock. The National Tournament will follow this listing.

Yes it should be spelled Thornthwaite.