How to identify Veined Metamorphic Rock

To correctly identify Veined Metamorphic Rock (Metamorphic rock with quartz or calcite veins), 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

   Host rock color varies widely (e.g., grey, black, green, red, white). Quartz veins are typically white, milky, or translucent. Calcite veins are typically white, cream, or light grey.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Host rock luster varies (e.g., dull, silky, vitreous, pearly). Quartz veins exhibit a vitreous (glassy) luster. Calcite veins exhibit a vitreous to dull luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Host rock texture is metamorphic (e.g., foliated, lineated, granoblastic). Veins are typically massive, granular, or crystalline, cutting across the host rock fabric.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz in veins often forms anhedral to subhedral crystals, sometimes euhedral if space allowed. Calcite in veins can form rhombohedral crystals, granular aggregates, or fibrous forms. Host rock minerals exhibit metamorphic crystal forms.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz has no cleavage, but conchoidal fracture. Calcite has perfect rhombohedral cleavage in three directions. Host rock minerals will exhibit their characteristic cleavage patterns.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Common in regions that have undergone significant tectonic deformation and metamorphism, such as mountain belts, subduction zones, and ancient cratons. Veins are often associated with fault zones, shear zones, and areas of intense fluid flow.

Key Facts

Hardness

Quartz: 7 on Mohs scale. Calcite: 3 on Mohs scale. Host rock hardness varies.

Specific Gravity

Quartz: 2.65 g/cm³. Calcite: 2.71 g/cm³. Host rock specific gravity varies.

Crystal System

Quartz: Trigonal. Calcite: Trigonal. Host rock minerals vary.

Color

Veins typically white, milky, or translucent. Host rock color is highly variable.

Luster

Vitreous (quartz) to vitreous/dull (calcite).

Transparency

Translucent to opaque (quartz and calcite veins).

Fracture

Conchoidal (quartz). Uneven to subconchoidal (calcite).

Cleavage

None (quartz). Perfect rhombohedral in 3 directions (calcite).

Composition

Veins primarily SiO2 (quartz) or CaCO3 (calcite). Host rock composition is highly variable, reflecting its protolith and metamorphic grade.

Physical characteristics

• Crystal Habit: Massive, granular, crystalline, sometimes euhedral crystals within veins. Host rock minerals exhibit metamorphic textures (e.g., schistose, gneissic, granoblastic).
• Cleavage Type: Quartz: None. Calcite: Perfect rhombohedral. Host rock minerals vary.
• Fracture Type: Quartz: Conchoidal. Calcite: Uneven to subconchoidal.
• Tenacity: Brittle (quartz and calcite).
• Luster Type: Vitreous (quartz) to vitreous/dull (calcite).

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