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Amazonite with Smoky Quartz is a striking mineral combination featuring the distinctive blue-green to greenish-blue variety of microcline feldspar (amazonite) intergrown with or adjacent to smoky quartz. The amazonite typically exhibits a vitreous luster and can range from translucent to opaque, often displaying fine white striations or perthitic exsolution lamellae. Smoky quartz, a variety of quartz, is characterized by its translucent to opaque gray to brownish-black color, also with a vitreous luster. This combination is highly sought after by mineral collectors and is often cut and polished for decorative items and jewelry.
How to Identify
- Color
- Amazonite: Blue-green to greenish-blue, sometimes with white streaks. Smoky Quartz: Translucent to opaque gray, brown, or black.
- Luster
- Vitreous (glassy) for both amazonite and smoky quartz.
- Texture
- Typically crystalline, often with large, well-formed crystals. Amazonite may show fine striations or perthitic textures. Smoky quartz can be massive or form distinct prismatic crystals.
- Crystal Form
- Amazonite: Triclinic, typically forming blocky to tabular crystals, often twinned. Smoky Quartz: Hexagonal, typically forming prismatic crystals with pyramidal terminations.
- Cleavage
- Amazonite: Two distinct cleavages at nearly 90 degrees (perfect on {001} and good on {010}). Smoky Quartz: No cleavage, exhibits conchoidal fracture.
- Geological Environment
- Granitic pegmatites, particularly those enriched in rare elements. Also found in some granites and syenites.
Key Facts
- Hardness: Amazonite: 6-6.5 (Mohs). Smoky Quartz: 7 (Mohs).
- Specific Gravity: Amazonite: 2.56-2.58. Smoky Quartz: 2.65-2.69.
- Crystal System: Amazonite: Triclinic. Smoky Quartz: Hexagonal (Trigonal).
- Color: Amazonite: Blue-green to greenish-blue. Smoky Quartz: Gray to brownish-black.
- Luster: Vitreous.
- Transparency: Translucent to opaque.
- Fracture: Amazonite: Uneven to conchoidal. Smoky Quartz: Conchoidal.
- Cleavage: Amazonite: Perfect on {001}, good on {010}. Smoky Quartz: None.
- Composition: Amazonite: KAlSi3O8 (Potassium Aluminum Silicate). Smoky Quartz: SiO2 (Silicon Dioxide).
Quick Check
- Color: Blue-green (amazonite) and gray to black (smoky quartz)
- Luster: Vitreous
- Streak: White (for both amazonite and smoky quartz)
Physical Characteristics
- Crystal Habit: Amazonite: Prismatic, tabular, blocky, often twinned. Smoky Quartz: Prismatic with pyramidal terminations, massive.
- Cleavage Type: Amazonite: Two distinct cleavages at nearly 90 degrees. Smoky Quartz: Absent.
- Fracture Type: Amazonite: Uneven to conchoidal. Smoky Quartz: Conchoidal.
- Tenacity: Brittle for both.
- Luster Type: Vitreous.
Formation
Amazonite with Smoky Quartz forms primarily in granitic pegmatites, which are late-stage igneous intrusions characterized by exceptionally large crystals. These pegmatites crystallize from residual magma that is rich in volatile components (like water, fluorine, and lithium) and incompatible elements. Amazonite (a variety of microcline feldspar) crystallizes from this melt, often in association with quartz. The smoky color in quartz is typically attributed to natural irradiation of aluminum impurities within the quartz crystal lattice. The blue-green color of amazonite is believed to be due to lead impurities and water within the crystal structure, or possibly due to radiation-induced color centers involving lead.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, beads, carvings), and as a collector's mineral specimen. The aesthetic contrast between the vibrant blue-green amazonite and the dark smoky quartz makes it highly desirable.
Age Distribution
Typically found in pegmatites of various ages, from Precambrian to Cenozoic, depending on the specific geological region.
Where to Find
Pikes Peak, Colorado, USA
Renowned for producing some of the finest amazonite and smoky quartz specimens, often found together in large, well-formed crystals within pegmatite pockets.
Minas Gerais, Brazil
A significant source of both amazonite and smoky quartz, often found in pegmatitic occurrences.
Ilmen Mountains, Russia
Historically important locality for amazonite, sometimes associated with quartz.
Madagascar
Produces high-quality amazonite, often found in pegmatites that can also yield smoky quartz.
Namibia
Known for its pegmatite deposits, which can contain both amazonite and smoky quartz.
Finding Tips
Target Pegmatites
Focus your search on granitic pegmatite outcrops, especially those known for producing feldspar and quartz minerals. Look for areas with coarse-grained igneous rocks.
Look for Associated Minerals
Amazonite and smoky quartz often occur with other pegmatite minerals such as albite, muscovite, biotite, and sometimes tourmaline or beryl. The presence of these minerals can indicate a promising locality.
Examine Rock Fractures and Pockets
Crystals often form in vugs, pockets, or fractures within the pegmatite body. Carefully inspect these areas for well-formed crystals.
Color and Luster
The distinctive blue-green color of amazonite and the dark, glassy luster of smoky quartz are key visual identifiers. Look for these characteristics in exposed rock faces or loose material.
Safety Precautions
When collecting in pegmatite environments, be aware of unstable rock, sharp edges, and potential for falling debris. Always wear appropriate safety gear, including hard hats, gloves, and eye protection. Some pegmatites can contain radioactive minerals, so it's advisable to use a Geiger counter if there's a possibility of such occurrences, and avoid prolonged exposure to unknown radioactive sources.
Similar Rocks
Amazonite
Microcline (variety Amazonite)
Also known as: Amazonstone
Smoky Quartz
Quartz (variety Smoky Quartz)
Also known as: Cairngorm
Albite with Quartz
Albite with Quartz
Also known as: Cleavelandite with Quartz
Scientific Classification
- Mineral Class
- Amazonite: Tectosilicate (Feldspar Group). Smoky Quartz: Tectosilicate (Quartz Group).
- Group
- Amazonite: Feldspar Group, Alkali Feldspar Subgroup. Smoky Quartz: Quartz Group.
- Crystal System
- Amazonite: Triclinic. Smoky Quartz: Hexagonal (Trigonal).
- Chemical Formula
- Amazonite: KAlSi3O8. Smoky Quartz: SiO2.
- Composition
- Amazonite: Potassium aluminum silicate. Smoky Quartz: Silicon dioxide.
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