Rock Sample Dichotomous Key

Rock sample dichotomous key

This dichotomous key separates four rock samples using observable texture and one simple test. A glassy surface points to obsidian. For the other rocks, a dilute-acid reaction distinguishes limestone. Visible sand-sized grains indicate sandstone, leaving granite as the crystalline, non-fizzing sample. The questions are arranged so each one narrows the remaining options. In a classroom, explain safety before using acid and substitute a different property if testing is not appropriate. Real rock identification can require additional observations, but a short key is useful for learning how classification decisions work. It gives readers a concise reference they can reuse when discussing the result with colleagues.

Tipo Árbol de decisionesNorma Howard-Raiffa / CART-sklearn / taxonomyMotor schematex-decisiontreeActualizado 24/9/2026

La solicitud

“A dichotomous key to identify obsidian, limestone, sandstone, and granite samples using glassy surface, acid reaction, and visible sand-sized grains.”

Entonces pruebaAdd a shale sample outcomeReplace the acid test with a hardness test

Qué hay en este dibujo

Lee las decisiones que hay detrás.

01Surface

Identify glassy obsidian first.

02Reaction

Use an acid test for limestone.

03Texture

Separate sandstone from crystalline granite.

Use for a supervised classroom rock-identification exercise.

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Preguntas frecuentes

Preguntas habituales

Why is acid used here?

Limestone commonly reacts with dilute acid because it contains calcite.

Is obsidian a mineral?

No. It is volcanic glass, classified as an igneous rock.

Can a key use tests and observations?

Yes, provided each step remains a clear two-way choice.