ROCK CLASSIFICATION

the three classes, 24 named rocks and the cycle that links them — after USGS and NPS

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Formats: A4 · A3 · A2
What you get: Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject: science · school · reference · classroom

Class definitions, subtypes, example rocks and the “over 2 mm” conglomerate threshold — USGS FAQ “What are igneous / sedimentary / metamorphic rocks?”; biologic and chemical examples and foliation — NPS geology pages. Grain swatches are schematic: they show relative size, not real texture. Checked 2026-08-13.

MARBLE USED TO BE LIMESTONE

Metamorphism melts nothing: as the USGS puts it, the rock does not melt — it is transformed into a denser, more compact one. So the marble on a windowsill is limestone recrystallised by heat and pressure, and hornfels is shale or sandstone simply baked by a hot intrusion.

Both pairs are proven by the build of this sheet: the parent rock of each metamorphic example really does stand in the sedimentary column next door.

On the sheet

Class definitions, subtypes, example rocks and the “over 2 mm” conglomerate threshold — USGS FAQ “What are igneous / sedimentary / metamorphic rocks?”; biologic and chemical examples and foliation — NPS geology pages. Grain swatches are schematic: they show relative size, not real texture. Checked 2026-08-13.
Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
Nothing about how it was made: the sheet carries only what the reader needs.

Printing

Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
White background and sparing fills — it prints on a home printer without draining the cartridge.
Margins of at least 10 mm: a home printer cannot print to the edge.
No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 7 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

ROCK CLASSIFICATION

MARBLE USED TO BE LIMESTONE

On the sheet

Printing

More like this

THE BEAUFORT SCALE

THE EIGHT BLOOD TYPES

RED CABBAGE pH INDICATOR

THE TEN CLOUD GENERA