5. _Dilute_ (10%) _hydrochloric acid_ (HCl), also known as _muriatic
acid_, to test carbonate rocks and minerals. You can buy a small
bottle at a drug store. Be extremely careful in handling this acid,
and keep it away from small children—it is a _POISON_. If you spill
any on yourself, it will burn your skin and eat holes in your clothes.
[Illustration: Hand lens.]
The rock and mineral identification charts on pages 24-41 will help you
to make the simple identification tests in a methodical way.
It is a good idea to have some system of labeling your rock and mineral
specimens. Some collectors carry note paper with them on field trips.
Then they can write down the location and, if possible, the name of the
rock or mineral. This information is either wrapped with the specimen or
stuck to it with tape. One way to label large collections is to put a
small spot of paint or fingernail polish on each of the rock and mineral
specimens. When the paint has dried, a number can be written on it in
black India ink. Then, on a file card, the name and the number of the
specimen can be written, together with the place where it was found, the
date of collection, and the name of the collector.