Showing 29 of 29 specimens
Granite
⚒️ Mohs 6–7
🌋 Cooled slowly underground
Basalt
⚒️ Mohs 6
🌋 Cooled lava flows
Obsidian
⚒️ Mohs 5–6
🌋 Super-fast cooled lava
Pumice
🌋 Frothy, gassy lava
Pegmatite
🌋 Very slow cooling
Limestone
⚒️ Mohs 3–4
🌋 Sea shells & skeletons
Sandstone
🌋 Cemented sand grains
Shale
⚒️ Mohs 3
🌋 Compacted mud & clay
Chalk
⚒️ Mohs 1
🌋 Tiny sea plankton
Coal
⚒️ Mohs 2–4
🌋 Buried ancient plants
Conglomerate
⚒️ Varies
🌋 Cemented pebbles
Marble
🌋 Heated limestone
Slate
🌋 Heated shale
Gneiss
🌋 Heated granite
Quartzite
⚒️ Mohs 7
🌋 Heated sandstone
Schist
⚒️ Mohs 4–5
Quartz
🌋 Most rock types
Diamond
⚒️ Mohs 10
🌋 Deep mantle, high pressure
Pyrite
⚒️ Mohs 6–6.5
🌋 Many environments
Halite (Salt)
⚒️ Mohs 2–2.5
🌋 Dried-up seas
Calcite
🌋 Limestone & caves
Talc
🌋 Metamorphic rocks
Magnetite
⚒️ Mohs 5.5–6.5
🌋 Igneous rocks
Ruby
⚒️ Mohs 9
🌋 Marble & basalt
Sapphire
🌋 Igneous & metamorphic rock
Emerald
⚒️ Mohs 7.5–8
🌋 Hydrothermal veins
Amethyst
🌋 Volcanic cavities
Opal
🌋 Silica-rich water
Turquoise
🌋 Dry, copper-rich rock
The Rock Cycle & Minerals
Hardness is measured on the Mohs scale (1 = softest, 10 = hardest).