Questions and answers

A mineral is a natural substance with a definite chemical composition and crystal structure. A rock is a natural aggregate of one or more minerals. If a hand lens shows grains of different colors and luster, you are most likely looking at a rock, such as granite.

The same mineral can come in different colors because of small impurities, and different minerals can look alike. Streak color is far more reliable: the powder a specimen leaves on unglazed porcelain is often more consistent than the color of the stone itself.

It is a scale of relative hardness proposed by the German mineralogist Friedrich Mohs in 1812. It has 10 reference minerals, from talc (1) to diamond (10); quartz sits at 7. The scale shows which mineral scratches which, not how many times harder one is than another.

Write down everything you got and mark the name with a question mark. The specimen may be weathered, dirty or made up of several minerals. In tricky cases it is more honest to show the find to a specialist than to force an answer.

It is convenient to start where nature has already gathered many different stones: river gravels and ocean beaches. Old mine spoil heaps are another option, but go there only where it is permitted and safe.

No. Collecting stones is prohibited in nature reserves and other protected areas. On private and industrial land, collecting is possible only with the owner's permission. Rules differ by country, so check the rules for the specific place before you go.

Stay away from cliff edges and overhanging slopes, and don't go down into canyons or quarries without permission and experience. Watch the weather: after rain, slopes crumble and stones near water get slippery.

A hammer isn't necessary at first: plenty of finds lie right on the surface. If you do break stones, wear a helmet and safety goggles, keep other people at a distance, and never strike a slope above you.

No. Sturdy stones can be rinsed with water, but soft, crumbly and water-soluble specimens are damaged by it. Clean them with a dry, soft brush, and sometimes it is better to leave them as they are.

The specimen number, its name or “unidentified,” the place of the find in general terms, the date and the finder's name. If you like, add your test results. Above all, write legibly and in permanent ink.

Some minerals are sensitive to light, others absorb moisture from the air or, on the contrary, dry out. Keep your collection in a cool, dry place away from sunlight and heating, and store especially delicate specimens in closed boxes.

Tiny grains and small crystals are easy to keep in small zip-top bags or clear jars. Put the label inside and repeat the number on the outside so you don't have to open every container.