Rock and Mineral Kits for Kids: The Mohs Scale, Streak Tests and Collecting Rules
Note: Some future links on this site may be affiliate links. We never claim hands-on testing; guides are researched from the public sources listed in each article.
How we wrote this: A guide based on standard mineral-identification methods and U.S. Bureau of Land Management collecting rules (source below). We have not personally tested these products. Professor Ploof is an AI-generated character and doesn't use or endorse any product. Adults should supervise hammering, and everyone should wear eye protection.
A box of labelled specimens is a nice start. Learning to identify a mystery rock yourself is better. Here are the classic tests and the gear for them.
The Mohs hardness scale
The Mohs scale ranks minerals from 1 (softest) to 10 (hardest) by which one scratches which. The ten reference minerals are talc (1), gypsum (2), calcite (3), fluorite (4), apatite (5), orthoclase feldspar (6), quartz (7), topaz (8), corundum (9) and diamond (10). The steps aren't equal: it's an ordering, not a measurement. Diamond is far harder than corundum.
Everyday testers
- A fingernail scratches minerals of about 2.5 or below.
- A copper coin is roughly 3 to 3.5.
- A steel nail or knife is roughly 5.5.
- Glass is roughly 5.5. If a mineral scratches glass, it's harder than that.
These values are approximate, so treat home results as clues rather than proof.
The streak test
Rub a mineral across an unglazed porcelain streak plate. The color of the powder (the streak) can differ from the color of the specimen. Hematite, for example, can look silver-gray or black but leaves a reddish-brown streak. Minerals harder than the plate won't leave a streak.
Other clues
- Luster: metallic, glassy, pearly, dull.
- Cleavage and fracture: does it break along flat planes, or in curved, shell-like surfaces?
- Magnetism: a small magnet picks out magnetite.
- Reaction to weak acid: calcite fizzes in dilute acid. This test needs adult supervision and eye protection, so many families skip it or use vinegar for a slow version.
What to look for in a kit
What to check
- Labelled specimens with names and, ideally, where they came from.
- Test tools included: streak plate, magnifier, a hardness set or scratch tools.
- A guide that teaches the tests, not just a list of names.
- Geode kits: check whether eye protection is included and how you're meant to open them. Some use a hammer, others a cracking tool.
(Look for: rock and mineral collection kit with identification guide) (Look for: geode cracking kit with safety goggles) (Look for: streak plate and mineral testing kit)
Where can you collect?
Rules depend on who manages the land. On public land managed by the U.S. Bureau of Land Management, regulations generally allow the public to collect reasonable amounts of rocks, mineral specimens and semiprecious gemstones for noncommercial purposes, with exceptions in certain areas (BLM, Rockhounding). National parks, state parks and private land have their own rules, and many parks prohibit collecting entirely. Check before you pick anything up, and get permission on private land.
A first rock-hounding outing
- Check the land manager's rules.
- Pack eye protection, gloves, a small brush, egg cartons or zip bags, and a notebook.
- Label each find with where and when you found it.
- Do the hardness and streak tests at home and compare with your guide.
Sources
- U.S. Bureau of Land Management, "Rockhounding": https://www.blm.gov/programs/recreation/rockhounding