How to identify Amazonite in Quartz

To correctly identify Amazonite in Quartz (Microcline (KAlSi3O8) variety amazonite 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

   Amazonite typically exhibits a distinctive blue-green to green color, often with white streaks or veins from albite exsolution lamellae. Quartz can be colorless, white (milky), or smoky. The combination will show these distinct color zones.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous for both amazonite and quartz. Amazonite may show a pearly luster on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granular to massive, with visible intergrowths of amazonite and quartz. Amazonite may show characteristic perthitic texture (intergrowth with albite) or fine striations on cleavage planes. Quartz will be glassy.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amazonite (microcline) typically forms anhedral to subhedral crystals, often tabular or blocky, within the quartz matrix. Quartz can be anhedral to euhedral, forming prismatic crystals with pyramidal terminations if space allowed, but often massive in pegmatites.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Amazonite (microcline) exhibits two distinct cleavages at approximately 90 degrees (perfect {001} and good {010}). Quartz has no cleavage, but exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Look for it in granitic pegmatites, which are often associated with larger granitic intrusions. These environments are characterized by very coarse-grained minerals.

Key Facts

Hardness

Amazonite: 6-6.5 (Mohs); Quartz: 7 (Mohs). The overall hardness will be dominated by quartz.

Specific Gravity

Amazonite: 2.56-2.58; Quartz: 2.65. The composite will be within this range.

Crystal System

Amazonite (Microcline): Triclinic; Quartz: Trigonal

Color

Blue-green to green (amazonite) and colorless, white, or smoky (quartz)

Luster

Vitreous to sub-vitreous; pearly on amazonite cleavage surfaces

Transparency

Translucent to opaque (amazonite); Transparent to translucent (quartz)

Fracture

Conchoidal (quartz); Uneven to conchoidal (amazonite)

Cleavage

Amazonite: Perfect {001} and good {010} at nearly 90 degrees; Quartz: None

Composition

KAlSi3O8 (Amazonite, a variety of Microcline) and SiO2 (Quartz)

Physical characteristics

• Crystal Habit: Amazonite: Anhedral to subhedral, tabular, blocky, massive; Quartz: Anhedral to euhedral, prismatic, massive
• Cleavage Type: Amazonite: Two directions, perfect {001} and good {010} at approximately 90 degrees; Quartz: None
• Fracture Type: Amazonite: Uneven to conchoidal; Quartz: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous to sub-vitreous; amazonite may show pearly on cleavage

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