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Amazonite in Quartz refers to specimens where the distinctive blue-green microcline variety, amazonite, is found intimately associated with or embedded within quartz. This can manifest as amazonite crystals growing alongside quartz crystals, or as amazonite inclusions within massive quartz. The combination often creates visually appealing pieces, with the vibrant color of amazonite contrasting with the often translucent to opaque white or gray quartz. The texture can range from granular to crystalline, depending on the specific growth habit of the minerals.
How to Identify
- Color
- Amazonite exhibits a distinctive blue-green to greenish-blue color, often with white streaks or mottling. The associated quartz can be colorless, white, gray, or smoky.
- Luster
- Amazonite typically has a vitreous to pearly luster on cleavage surfaces. Quartz has a vitreous luster.
- Texture
- Can be massive, granular, or crystalline. Individual amazonite crystals may be blocky or tabular. Quartz can be anhedral (massive) or euhedral (well-formed crystals).
- Crystal Form
- Amazonite (microcline) forms triclinic crystals, often pseudo-orthorhombic, typically blocky or tabular. Quartz forms hexagonal prisms with pyramidal terminations.
- Cleavage
- Amazonite (microcline) exhibits two distinct cleavages at nearly 90 degrees (perfect {001} and good {010}). Quartz has no cleavage, but exhibits conchoidal fracture.
- Geological Environment
- Primarily found in granitic pegmatites, which are late-stage igneous intrusions. Also occurs in some granites and syenites, and occasionally in metamorphic rocks.
Key Facts
- Hardness: Amazonite (Microcline): 6-6.5 on Mohs scale; Quartz: 7 on Mohs scale
- Specific Gravity: Amazonite (Microcline): 2.56-2.58; Quartz: 2.65
- Crystal System: Amazonite (Microcline): Triclinic; Quartz: Trigonal
- Color: Blue-green to greenish-blue (amazonite); Colorless, white, gray, smoky (quartz)
- Luster: Vitreous to pearly (amazonite); Vitreous (quartz)
- Transparency: Translucent to opaque (amazonite); Transparent to opaque (quartz)
- Fracture: Uneven to conchoidal (amazonite); Conchoidal (quartz)
- Cleavage: Amazonite (Microcline): Perfect {001}, good {010} at nearly 90 degrees; Quartz: None
- Composition: Amazonite: KAlSi3O8 (Potassium Aluminum Silicate); Quartz: SiO2 (Silicon Dioxide)
Quick Check
- Color: Blue-green (amazonite) with colorless, white, or smoky (quartz)
- Luster: Vitreous to pearly (amazonite), Vitreous (quartz)
- Streak: White (both amazonite and quartz)
Physical Characteristics
- Crystal Habit: Amazonite: Blocky, tabular, massive; Quartz: Prismatic, massive, granular
- Cleavage Type: Amazonite: Two directions at nearly 90 degrees; Quartz: Absent
- Fracture Type: Amazonite: Uneven to conchoidal; Quartz: Conchoidal
- Tenacity: Brittle (both amazonite and quartz)
- Luster Type: Vitreous to pearly (amazonite); Vitreous (quartz)
Formation
Amazonite (a variety of microcline feldspar) forms in granitic pegmatites, which are coarse-grained igneous rocks that crystallize from residual magma enriched in volatile components. Quartz is a ubiquitous mineral in these environments. The 'Amazonite in Quartz' specimens typically represent intergrowths or inclusions of amazonite within a quartz matrix, or distinct crystals of both minerals occurring together within the same pegmatite body. The characteristic blue-green color of amazonite is attributed to small amounts of lead (Pb) and water (H2O) within the crystal lattice, rather than copper as previously thought.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, beads, carvings), and in jewelry. Due to its aesthetic appeal, it is also collected by mineral enthusiasts. It has no significant industrial uses beyond its ornamental value.
Age Distribution
Precambrian to Cenozoic, typically associated with granitic intrusions of various ages.
Where to Find
Pikes Peak, Colorado, USA
Renowned for producing some of the finest amazonite crystals, often associated with smoky quartz in pegmatites.
Miass, Ilmen Mountains, Russia
Historically significant locality for large amazonite crystals.
Minas Gerais, Brazil
Known for various pegmatite minerals, including amazonite and quartz.
Madagascar
Produces significant quantities of amazonite, often found in pegmatitic contexts.
Virginia, USA
Localities in Amelia County are known for amazonite-bearing pegmatites.
Finding Tips
Target Pegmatites
Focus your search on granitic pegmatite outcrops, especially those known for feldspar mineralization. Look for coarse-grained igneous rocks.
Look for Blue-Green Color
The distinctive blue-green color of amazonite is the primary visual indicator. It can range from pale to intense.
Check for Cleavage
If you find a blue-green mineral, test for the two nearly perpendicular cleavages characteristic of feldspar (amazonite). Quartz will not exhibit this cleavage.
Associated Minerals
Amazonite in quartz is often found with other pegmatite minerals such as muscovite, biotite, tourmaline, and garnet.
Similar Rocks
Feldspar in Quartz
Various Feldspar (e.g., Orthoclase, Plagioclase) in Quartz (SiO2)
Also known as: Various feldspar-quartz intergrowths
Graphic Granite
Quartz (SiO2) and Feldspar (KAlSi3O8 or NaAlSi3O8)
Also known as: Hebrew Stone
Blue Quartz
Quartz (SiO2) with inclusions (e.g., Dumortierite)
Also known as: Dumortierite Quartz
Scientific Classification
- Mineral Class
- Tectosilicate
- Group
- Feldspar Group (Amazonite); Quartz Group (Quartz)
- Crystal System
- Triclinic (Amazonite); Trigonal (Quartz)
- Chemical Formula
- KAlSi3O8 (Amazonite); SiO2 (Quartz)
- Composition
- Potassium Aluminum Silicate (Amazonite); Silicon Dioxide (Quartz)
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