How to identify Marble

To correctly identify Marble (Metamorphic rock, primarily calcite or dolomite), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically white, but can be pink, red, yellow, green, brown, gray, or black due to impurities. Often exhibits veining or mottling.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to dull, depending on the grain size and presence of impurities. Polished surfaces have a high vitreous luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granoblastic (equigranular, interlocking crystals), non-foliated. Grain size can range from fine to coarse. May show saccharoidal (sugar-like) texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Individual crystals are typically anhedral (lacking well-formed faces) due to mutual interference during recrystallization. Calcite and dolomite crystals are rhombohedral.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Calcite and dolomite exhibit perfect rhombohedral cleavage in three directions, which can be observed in individual crystals within the marble.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in metamorphic terrains, often associated with regional metamorphic belts (e.g., mountain ranges) or contact metamorphic aureoles around igneous intrusions. Occurs in areas where limestone or dolostone protoliths have been subjected to heat and pressure.

Key Facts

Hardness

3 (calcite) to 3.5-4 (dolomite) on the Mohs scale

Specific Gravity

2.71 g/cm³ (calcite marble) to 2.85 g/cm³ (dolomite marble)

Crystal System

Trigonal (for calcite and dolomite)

Color

Pure white; impurities cause pink, red, yellow, green, brown, gray, black

Luster

Vitreous to dull; polished surfaces are highly vitreous

Transparency

Opaque to translucent

Fracture

Uneven to conchoidal

Cleavage

Perfect rhombohedral in three directions (for calcite and dolomite)

Composition

Primarily calcite (CaCO3) or dolomite (CaMg(CO3)2); may contain quartz, mica, tremolite, diopside, forsterite, garnet, wollastonite, pyrite, graphite, iron oxides.

Physical characteristics

• Crystal Habit: Granular, interlocking mosaic of anhedral crystals; individual crystals are typically rhombohedral.
• Cleavage Type: Perfect rhombohedral (3 directions at ~75° and ~105°)
• Fracture Type: Uneven to subconchoidal
• Tenacity: Brittle
• Luster Type: Vitreous to dull

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