How to identify Marble

To correctly identify Marble (Metamorphic rock (recrystallized 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 in its purest form, but can be pink, red, yellow, green, black, gray, or variegated due to impurities. Veining is common.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to dull, depending on the grain size and presence of impurities. Polished surfaces exhibit 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.

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 growth, forming a mosaic.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Calcite and dolomite, the primary minerals, exhibit perfect rhombohedral cleavage in three directions, which can sometimes be observed in larger grains within the marble.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Formed in regional metamorphic belts associated with convergent plate boundaries (orogenic belts) or by contact metamorphism adjacent to igneous intrusions. Occurs in areas where thick sequences of limestone or dolostone have been subjected to elevated temperatures and pressures.

Key Facts

Hardness

3-4 on Mohs scale (for calcite-rich marble); 3.5-4 on Mohs scale (for dolomite-rich marble).

Specific Gravity

2.7-2.9 (for calcite marble); 2.8-2.9 (for dolomitic marble).

Crystal System

Trigonal (for calcite and dolomite).

Color

Variable, from pure white to various hues and patterns.

Luster

Vitreous to dull.

Transparency

Opaque to translucent, rarely transparent in very pure, coarse-grained varieties.

Fracture

Uneven to subconchoidal.

Cleavage

Perfect rhombohedral in three directions (characteristic of calcite and dolomite).

Composition

Primarily calcite (CaCO3) or dolomite (CaMg(CO3)2), with various accessory minerals.

Physical characteristics

• Crystal Habit: Granular, massive, interlocking anhedral crystals.
• Cleavage Type: Perfect rhombohedral (3 directions at 74° and 106°).
• Fracture Type: Uneven to subconchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous to dull.

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