How to identify Granite with Quartz Vein

To correctly identify Granite with Quartz Vein (Granite (igneous rock) with Quartz (SiO2)), 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

   Granite: Typically light-colored, ranging from white, gray, pink, or red, depending on the feldspar composition. Quartz Vein: Usually milky white, translucent, or clear, sometimes stained by iron oxides (yellow, brown, red).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Granite: Overall dull to sub-vitreous due to mixed mineral lusters. Quartz Vein: Vitreous (glassy).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granite: Phaneritic (coarse-grained), equigranular to porphyritic. Quartz Vein: Crystalline, often massive or drusy, with individual quartz crystals visible.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Granite: Anhedral to subhedral crystals of quartz, feldspar, and mica. Quartz Vein: Anhedral to euhedral quartz crystals, often forming interlocking masses or prismatic crystals if space allowed during growth.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Granite: Feldspars exhibit good cleavage (2 directions at ~90 degrees), micas exhibit perfect basal cleavage (1 direction). Quartz: No cleavage, conchoidal fracture. Quartz Vein: No cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Intrusive igneous environments, typically associated with continental crust, mountain-building events (orogenies), and subduction zones. Quartz veins form in fractures within these granitic bodies, often in brittle deformation regimes, due to hydrothermal fluid circulation.

Key Facts

Hardness

Granite: 6-7 (Mohs, average of constituent minerals). Quartz Vein: 7 (Mohs).

Specific Gravity

Granite: 2.65-2.75 g/cm³. Quartz Vein: 2.65 g/cm³.

Crystal System

Granite: Polycrystalline aggregate (individual minerals have their own systems: Quartz - Trigonal, Feldspar - Monoclinic/Triclinic, Mica - Monoclinic). Quartz Vein: Trigonal (for quartz).

Color

Granite: Variable (white, gray, pink, red). Quartz Vein: Milky white, translucent, clear.

Luster

Granite: Dull to sub-vitreous. Quartz Vein: Vitreous.

Transparency

Granite: Opaque to translucent. Quartz Vein: Translucent to transparent.

Fracture

Granite: Irregular to conchoidal (quartz). Quartz Vein: Conchoidal.

Cleavage

Granite: Good in feldspar and mica, none in quartz. Quartz Vein: None.

Composition

Granite: Predominantly quartz (20-60%), alkali feldspar (35-90% of total feldspar), plagioclase feldspar (10-65% of total feldspar), and micas/amphiboles. Quartz Vein: Nearly 100% SiO2 (silicon dioxide).

Physical characteristics

• Crystal Habit: Granite: Granular, interlocking anhedral to subhedral crystals. Quartz Vein: Massive, crystalline, sometimes prismatic (euhedral) if vugs are present.
• Cleavage Type: Granite: Good in feldspar (two directions at ~90°), perfect basal in mica (one direction). Quartz: None. Quartz Vein: None.
• Fracture Type: Granite: Irregular to conchoidal (quartz component). Quartz Vein: Conchoidal.
• Tenacity: Granite: Brittle. Quartz Vein: Brittle.
• Luster Type: Granite: Dull to sub-vitreous. Quartz Vein: Vitreous.

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