Amazonite in Quartz

Igneous (pegmatitic)

Microcline (KAlSi3O8) variety amazonite with Quartz (SiO2)

Also known as: Amazonstone in Quartz

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Description

Amazonite in Quartz is a composite mineral specimen featuring the distinctive blue-green to green color of amazonite (a variety of microcline feldspar) intergrown with or embedded within a matrix of colorless to milky white or smoky quartz. The amazonite component is a tectosilicate mineral, while quartz is a silicate mineral. The combination creates a visually appealing material, often with contrasting colors and textures. The amazonite may appear as distinct crystals, irregular masses, or graphic intergrowths within the quartz.

How to Identify

Color: 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.
Luster: Vitreous to sub-vitreous for both amazonite and quartz. Amazonite may show a pearly luster on cleavage surfaces.
Texture: 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.
Crystal Form: 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.
Cleavage: Amazonite (microcline) exhibits two distinct cleavages at approximately 90 degrees (perfect {001} and good {010}). Quartz has no cleavage, but exhibits conchoidal fracture.
Geological Environment: 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)

Quick Check

Color: Blue-green to green (amazonite) with colorless, white, or smoky (quartz)
Luster: Vitreous to sub-vitreous
Streak: White (for both amazonite and 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

Formation

Amazonite in Quartz forms primarily in granitic pegmatites, which are coarse-grained igneous rocks that crystallize from residual magma enriched in incompatible elements and volatiles (like water, fluorine, and lithium). The amazonite (a variety of microcline feldspar) crystallizes alongside quartz, often in graphic intergrowths or as distinct crystals within the quartz matrix. The characteristic blue-green color of amazonite is attributed to small amounts of lead (Pb) within the crystal lattice, possibly substituting for potassium, and structural water, which creates color centers when irradiated.

Usage

Primarily used as an ornamental stone, for cabochons, beads, carvings, and decorative objects. Its attractive color makes it popular in jewelry. It is also collected by mineral enthusiasts.

Age Distribution

Typically found in granitic pegmatites, which can range from Precambrian to Cenozoic, with many significant deposits being Mesozoic or Paleozoic.

Where to Find

Pikes Peak, Colorado, USA

Famous for producing some of the finest deep blue-green amazonite crystals, often found in association with smoky quartz and albite in pegmatite pockets.

Minas Gerais, Brazil

Known for various pegmatite minerals, including amazonite, sometimes found with quartz.

Ilmen Mountains, Russia

Historically significant locality for amazonite, often found in pegmatites.

Ambatofinandrahana, Madagascar

Produces high-quality amazonite, frequently intergrown with quartz.

Muzo, Colombia

While primarily known for emeralds, some pegmatitic occurrences can yield amazonite.

Ethiopia

Newer discoveries of amazonite in quartz have been reported.

Finding Tips

Target Pegmatites

Focus your search on granitic pegmatite outcrops. These are typically coarse-grained igneous rocks, often found as dikes or sills intruding into other rock types.

Look for Feldspar and Quartz

Identify areas rich in large feldspar crystals (especially potassium feldspar) and quartz. Amazonite is a variety of microcline, a potassium feldspar.

Color Clues

Keep an eye out for the distinctive blue-green color of amazonite. It can range from pale to intense, and may be unevenly distributed.

Associated Minerals

Amazonite in quartz is often found with other pegmatite minerals such as albite, muscovite, biotite, garnet, and sometimes tourmaline or beryl.

Fracture Zones

Examine weathered pegmatite zones or areas where the rock has fractured, as these can expose fresh surfaces of the minerals.

Similar Rocks

Chrysoprase

Chalcedony (SiO2) variety chrysoprase

Also known as: Australian Jade

Turquoise

CuAl6(PO4)4(OH)8·4H2O

Also known as: Callais

Jadeite

NaAlSi2O6

Also known as: Burmese Jade

Serpentine

(Mg,Fe)3Si2O5(OH)4

Also known as: New Jade

Scientific Classification

Mineral Class: Tectosilicates
Group: Feldspar Group (Amazonite/Microcline); Quartz Group (Quartz)
Crystal System: Triclinic (Amazonite/Microcline); Trigonal (Quartz)
Chemical Formula: KAlSi3O8 (Amazonite) + SiO2 (Quartz)
Composition: Potassium aluminum silicate (Amazonite) and Silicon dioxide (Quartz)

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