Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Amazonite is a tectosilicate mineral, a variety of microcline feldspar, known for its distinctive blue-green to green color. It typically forms in well-formed crystals within pegmatites. Orange Calcite is a carbonate mineral, a common form of calcium carbonate, characterized by its vibrant orange to yellowish-orange hues. It often forms in massive, granular, or rhombohedral crystalline habits. When found together, these two minerals create a striking contrast in color and texture, though they rarely occur in direct geological association in their primary formation environments. Combinations are typically due to lapidary work or specific secondary mineralization.
How to Identify
- Color
- Amazonite: Distinctive blue-green to green, sometimes with white streaks or inclusions. Orange Calcite: Vibrant orange, yellowish-orange, or reddish-orange.
- Luster
- Amazonite: Vitreous to pearly. Orange Calcite: Vitreous to resinous, sometimes dull in massive forms.
- Texture
- Amazonite: Typically smooth, often with a granular or blocky appearance in massive forms. Orange Calcite: Can be smooth, granular, or crystalline with distinct rhombohedral faces.
- Crystal Form
- Amazonite: Triclinic system, often forms prismatic or tabular crystals, sometimes massive. Orange Calcite: Trigonal system, commonly forms rhombohedral crystals, also massive, granular, fibrous, or stalactitic.
- Cleavage
- Amazonite: Perfect in two directions at nearly 90 degrees (basal and prismatic). Orange Calcite: Perfect rhombohedral cleavage in three directions, producing characteristic rhomb-shaped fragments.
- Geological Environment
- Amazonite: Granitic pegmatites, often associated with quartz, albite, and mica. Orange Calcite: Sedimentary rocks (limestone, marble), hydrothermal veins, caves (speleothems), and as a secondary mineral in various rock types.
Key Facts
- Hardness: Amazonite: 6-6.5 (Mohs). Orange Calcite: 3 (Mohs).
- Specific Gravity: Amazonite: 2.56-2.58. Orange Calcite: 2.71.
- Crystal System: Amazonite: Triclinic. Orange Calcite: Trigonal.
- Color: Amazonite: Blue-green to green. Orange Calcite: Orange, yellowish-orange, reddish-orange.
- Luster: Amazonite: Vitreous to pearly. Orange Calcite: Vitreous to resinous.
- Transparency: Amazonite: Translucent to opaque. Orange Calcite: Transparent to translucent.
- Fracture: Amazonite: Uneven to conchoidal. Orange Calcite: Conchoidal to uneven.
- Cleavage: Amazonite: Perfect in two directions at nearly 90 degrees. Orange Calcite: Perfect rhombohedral in three directions.
- Composition: Amazonite: Potassium aluminum silicate (KAlSi3O8). Orange Calcite: Calcium carbonate (CaCO3).
Quick Check
- Color: Amazonite: Blue-green to green. Orange Calcite: Orange to yellowish-orange.
- Luster: Amazonite: Vitreous to pearly. Orange Calcite: Vitreous to resinous.
- Streak: Amazonite: White. Orange Calcite: White.
Physical Characteristics
- Crystal Habit: Amazonite: Prismatic, tabular, massive. Orange Calcite: Rhombohedral, massive, granular, stalactitic.
- Cleavage Type: Amazonite: Basal and prismatic. Orange Calcite: Rhombohedral.
- Fracture Type: Amazonite: Uneven to conchoidal. Orange Calcite: Conchoidal to uneven.
- Tenacity: Amazonite: Brittle. Orange Calcite: Brittle.
- Luster Type: Amazonite: Vitreous to pearly. Orange Calcite: Vitreous to resinous.
Formation
Amazonite: Forms in granitic pegmatites, which are coarse-grained igneous rocks that crystallize from residual magma enriched in volatile components. The distinctive blue-green color is attributed to small amounts of lead (Pb) within the crystal lattice, often requiring specific cooling conditions. Orange Calcite: Primarily forms through the precipitation of calcium carbonate from aqueous solutions. This can occur in marine environments (e.g., shell fragments, coral reefs), caves (stalactites, stalagmites), hot springs, or as a secondary mineral in hydrothermal veins and metamorphic rocks. The orange color is typically due to the presence of iron impurities (e.g., hematite, goethite) or organic inclusions.
Usage
Amazonite: Primarily used as a gemstone, for ornamental carvings, and in jewelry. It is also collected by mineral enthusiasts. Orange Calcite: Used as an ornamental stone, in carvings, and as a source of calcium carbonate for industrial applications (e.g., cement, lime, agriculture). It is also popular in lapidary arts and for metaphysical purposes.
Age Distribution
Amazonite: Found in pegmatites of various ages, often associated with granitic intrusions from Precambrian to Cenozoic. Orange Calcite: Forms in sedimentary environments, hydrothermal veins, and metamorphic settings, ranging from ancient Precambrian to modern-day deposits.
Where to Find
Amazonite: Pikes Peak, Colorado, USA
Renowned for producing some of the finest deep blue-green amazonite crystals, often associated with smoky quartz.
Amazonite: Minas Gerais, Brazil
Significant source of amazonite, often found in large masses and crystals within pegmatite deposits.
Amazonite: Ilmen Mountains, Russia
Historical source of high-quality amazonite, particularly from the Ural Mountains region.
Amazonite: Amelia Courthouse, Virginia, USA
Known for its pegmatite deposits yielding amazonite and other feldspar minerals.
Orange Calcite: Mexico
Major producer of orange calcite, often found in large, translucent masses suitable for carving.
Orange Calcite: USA (various states)
Found in numerous localities, particularly in limestone caves (e.g., Missouri, Arkansas) and hydrothermal deposits.
Orange Calcite: China
Significant source of various calcite forms, including orange varieties, often from mining operations.
Orange Calcite: Peru
Known for its diverse mineral deposits, including occurrences of orange calcite.
Finding Tips
Amazonite in Pegmatites
Look for amazonite in granitic pegmatite dikes. These are often found in areas with significant igneous activity and can be identified by their unusually large crystal sizes and diverse mineral assemblages. Search for areas with exposed bedrock or old mine dumps.
Orange Calcite in Sedimentary and Hydrothermal Settings
Orange calcite can be found in limestone quarries, caves, and areas with hydrothermal alteration. In caves, look for stalactites, stalagmites, and flowstone. In sedimentary environments, it may occur as veins or replacement minerals. Always obtain permission before entering private land or caves.
Color and Luster Identification
Amazonite's distinct blue-green color is a primary identifier. Orange calcite's vibrant orange hue and vitreous luster are key. Be aware that both minerals can have variations in color intensity.
Cleavage Test
For Amazonite, observe the two perfect cleavages at nearly 90 degrees. For Orange Calcite, the perfect rhombohedral cleavage is a definitive test; a small piece will break into rhomb-shaped fragments. This can be done carefully with a rock hammer or by observing natural breaks.
Hardness Test (for differentiation)
Amazonite (6-6.5 on Mohs scale) is significantly harder than Orange Calcite (3 on Mohs scale). Amazonite will scratch glass, while calcite will not and can be scratched by a copper coin. This is a crucial differentiating factor.
Acid Test (for Calcite)
Orange Calcite will effervesce (fizz) vigorously when a drop of dilute hydrochloric acid (HCl) is applied to its surface, due to the release of carbon dioxide. Amazonite will not react to acid. Always handle acids with extreme caution and appropriate safety gear.
Similar Rocks
Turquoise
CuAl6(PO4)4(OH)8·4H2O
Also known as: Callais
Chrysocolla
(Cu,Al)2H2Si2O5(OH)4·nH2O
Also known as: Gem Silica
Blue Calcite
CaCO3
Also known as: Caribbean Calcite
Aragonite
CaCO3
Also known as: Flos Ferri
Scientific Classification
- Mineral Class
- Amazonite: Tectosilicate (Feldspar Group). Orange Calcite: Carbonate.
- Group
- Amazonite: Feldspar Group (specifically, Microcline). Orange Calcite: Calcite Group.
- Crystal System
- Amazonite: Triclinic. Orange Calcite: Trigonal.
- Chemical Formula
- Amazonite: KAlSi3O8. Orange Calcite: CaCO3.
- Composition
- Amazonite: Potassium, aluminum, silicon, oxygen. Orange Calcite: Calcium, carbon, oxygen.
Explore Amazonite and Orange Calcite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.