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K2 Jasper is a distinctive rock characterized by a white to off-white, fine-grained granitic matrix with contrasting spherical or irregular inclusions of bright blue azurite. The granite component is typically composed of quartz, feldspar (orthoclase and/or plagioclase), and mica (biotite or muscovite). The azurite inclusions can range in size from pinpoint dots to several centimeters in diameter, creating a striking 'polka-dot' or 'snowball' effect. Despite its common name, it is not a true jasper, which is a microcrystalline variety of quartz. The 'K2' refers to the K2 mountain in the Karakoram range, near which it was first discovered.
How to Identify
- Color
- White to off-white granitic matrix with distinct, often spherical, bright blue azurite inclusions. The blue can range from sky blue to deep azure.
- Luster
- Granite matrix: Vitreous to dull (quartz, feldspar). Azurite: Vitreous to dull, sometimes earthy.
- Texture
- Granitic matrix is typically fine-grained, phaneritic (visible crystals). Azurite inclusions are often massive or granular within the granite.
- Crystal Form
- Granite: Anhedral to subhedral interlocking crystals of quartz, feldspar, mica. Azurite: Typically massive, granular, or botryoidal within the granite; rarely as distinct monoclinic crystals.
- Cleavage
- Granite: Feldspar exhibits good cleavage (2 directions at ~90°), mica has perfect basal cleavage. Quartz has no cleavage. Azurite: Good cleavage in one direction, fair in another (monoclinic).
- Geological Environment
- Intrusive igneous environments where granitic magmas have cooled slowly, followed by hydrothermal alteration or fluid infiltration that introduced copper-rich solutions, leading to the secondary formation of azurite within the granite.
Key Facts
- Hardness: Granite matrix: 6-7 (Mohs). Azurite inclusions: 3.5-4 (Mohs). Overall rock hardness is variable.
- Specific Gravity: Approximately 2.6-3.0 g/cm³ (variable depending on azurite content).
- Crystal System: Granite: Polycrystalline aggregate (quartz: trigonal, feldspar: monoclinic/triclinic, mica: monoclinic). Azurite: Monoclinic.
- Color: White to grey matrix with bright azure blue to deep blue spots.
- Luster: Vitreous to dull (granite), vitreous to earthy (azurite).
- Transparency: Opaque.
- Fracture: Granite: Uneven to conchoidal (quartz). Azurite: Conchoidal.
- Cleavage: Granite: Feldspar (good in 2 directions), Mica (perfect basal). Azurite: Good in one direction, fair in another.
- Composition: Granite (primarily quartz, feldspar, mica) with inclusions of Azurite (Cu3(CO3)2(OH)2).
Quick Check
- Color: White/grey with bright blue spots
- Luster: Vitreous to dull
- Streak: Granite: White. Azurite: Light blue
Physical Characteristics
- Crystal Habit: Granite: Granular, massive. Azurite: Massive, granular, botryoidal, rarely prismatic crystals.
- Cleavage Type: Granite: Feldspar (prismatic), Mica (basal). Azurite: Prismatic.
- Fracture Type: Granite: Uneven to conchoidal. Azurite: Conchoidal.
- Tenacity: Brittle.
- Luster Type: Vitreous to dull (granite), vitreous to earthy (azurite).
Formation
K2 Jasper is primarily a granitic rock, an intrusive igneous rock formed from the slow crystallization of magma beneath the Earth's surface. The distinctive blue 'spots' are inclusions of azurite, a secondary copper carbonate mineral. These azurite inclusions form later, typically through the alteration of primary copper-bearing minerals within the granite or from hydrothermal fluids percolating through fractures in the granite, depositing azurite in localized concentrations.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, spheres, carvings), and in jewelry. Its unique appearance makes it popular in the metaphysical and collector markets.
Age Distribution
Variable, depending on the age of the granite intrusion. The azurite mineralization is secondary and post-dates the granite formation.
Where to Find
Skardu area, Northern Areas, Pakistan
The primary and most well-known source, found near the base of K2 mountain in the Karakoram range. This is the type locality for K2 Jasper.
Finding Tips
Visual Identification
Look for the characteristic white to grey granitic background with distinct, often rounded, bright blue spots. The blue color is key to identifying azurite.
Hardness Test (Caution)
The granite matrix will be relatively hard (Mohs 6-7 for quartz and feldspar). The azurite inclusions are much softer (Mohs 3.5-4). A careful scratch test on an inconspicuous area might reveal the difference, but be cautious not to damage the specimen.
Acid Test (Not Recommended for Collectors)
Azurite (a carbonate) will effervesce with dilute hydrochloric acid. This test is destructive and not recommended for finished specimens or valuable rough. It can confirm the presence of azurite but is not necessary for identification.
Specific Gravity
The overall specific gravity will be a composite of granite (2.6-2.7 g/cm³) and azurite (3.77-3.89 g/cm³), making it slightly denser than typical granite if azurite content is significant.
Similar Rocks
Dalmatian Jasper
Porphyritic aplite/rhyolite with arfvedsonite/aegirine inclusions
Also known as: Dalmatian Stone
Orbicular Jasper
Microcrystalline quartz with various mineral inclusions
Also known as: Ocean Jasper
Blue Spot Jasper
Microcrystalline quartz with various mineral inclusions
Also known as: Blue Spot Stone
Scientific Classification
- Mineral Class
- Granite: Igneous rock. Azurite: Carbonate mineral.
- Group
- Granite: Felsic intrusive igneous rock. Azurite: Hydrous copper carbonate.
- Crystal System
- Granite: Polycrystalline aggregate. Azurite: Monoclinic.
- Chemical Formula
- Granite: Complex silicate mixture. Azurite: Cu3(CO3)2(OH)2.
- Composition
- Granite: SiO2, Al2O3, K2O, Na2O, CaO, FeO, MgO. Azurite: Copper, Carbon, Oxygen, Hydrogen.
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