How to identify Amazonite in matrix

To correctly identify Amazonite in matrix (Microcline (variety amazonite) with host rock), 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

   Varies from pale greenish-blue to intense turquoise-green. The matrix is typically white, grey, or translucent (quartz).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly on cleavage surfaces for amazonite; matrix minerals can be vitreous (quartz) or dull (weathered feldspar).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Coarse-grained, often with distinct interlocking crystals of amazonite, quartz, and other feldspars. Amazonite crystals can be anhedral to subhedral.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amazonite typically forms anhedral to subhedral masses or blocky crystals within the pegmatite. It belongs to the triclinic crystal system. The matrix minerals (quartz, albite) will also exhibit their characteristic crystal forms.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Amazonite (microcline) exhibits two distinct cleavages at approximately 90 degrees (89°30' to be precise), characteristic of feldspars. The matrix minerals will have their own cleavage properties (e.g., quartz has no cleavage).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Exclusively found in granitic pegmatites, which are late-stage differentiates of granitic magmas. These pegmatites often intrude into older igneous or metamorphic rocks.

Key Facts

Hardness

6 to 6.5 on the Mohs scale (for amazonite and other feldspars); 7 for quartz.

Specific Gravity

2.56 - 2.58 g/cm³ (for amazonite).

Crystal System

Triclinic (for amazonite/microcline).

Color

Blue-green to turquoise-green (amazonite).

Luster

Vitreous to pearly.

Transparency

Translucent to opaque.

Fracture

Uneven to conchoidal (for amazonite).

Cleavage

Perfect in two directions at nearly 90 degrees (for amazonite).

Composition

KAlSi3O8 (Potassium Aluminum Silicate) with trace lead for color.

Physical characteristics

• Crystal Habit: Typically anhedral to subhedral masses, blocky crystals, or tabular crystals within the pegmatite matrix.
• Cleavage Type: Perfect basal {001} and good prismatic {010} cleavage, intersecting at approximately 89°30'.
• Fracture Type: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous to pearly on cleavage surfaces.

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