Rocks and Minerals

A mineral is a specific, orderly arrangement of atoms, and that arrangement, not just the atoms themselves, decides its properties. Diamond and graphite are both pure carbon, but diamond's atoms lock into a rigid 3D network, while graphite's atoms stack in weak, slippery sheets. That's why diamond scores 10 on the Mohs hardness scale, the hardest known mineral, while graphite scores around 1 to 2, soft enough to leave marks on paper, like pencil lead.

Rocks are built from minerals, and the rock cycle describes how rocks transform into other rock types under heat, pressure, and weathering. Molten rock cools and crystallizes into igneous rock. Weathering breaks any rock into sediment, which compacts and cements into sedimentary rock. Heat and pressure underground, without melting, can squeeze either type into metamorphic rock. Enough heat melts rock back into magma, and the cycle starts over. None of these paths is one-way, which is why the same material can show up as granite, then sand, then sandstone, then schist, depending on what it has been through.

Texture within igneous rock tells you about cooling speed, connecting directly back to crystal formation. Magma that cools slowly deep underground gives atoms time to migrate and build large, visible crystals, like in granite. Lava that erupts and cools in seconds at the surface freezes before crystals can grow, leaving a fine-grained or glassy texture, like in basalt or obsidian. Same chemistry, totally different look, purely from cooling rate.