Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Kambaba Jasper is a distinctive sedimentary rock characterized by its dark green to black background with swirling patterns, orbicular structures, or concentric rings of lighter green, black, or sometimes brown. These patterns are the fossilized remains of ancient stromatolites, which are layered accretionary structures formed in shallow water by the growth of microbial communities, primarily cyanobacteria. The rock is predominantly composed of microcrystalline quartz (chert/jasper) with various mineral inclusions that contribute to its color and pattern.
How to Identify
- Color
- Dark green to black with swirling patterns, orbicular structures, or concentric rings of lighter green, black, or sometimes brown.
- Luster
- Dull to waxy, vitreous when polished.
- Texture
- Fine-grained, dense, often with visible orbicular or layered structures.
- Crystal Form
- Cryptocrystalline (microcrystalline quartz), no macroscopic crystal forms.
- Cleavage
- None, exhibits conchoidal fracture.
- Geological Environment
- Formed in shallow marine environments where microbial mats (stromatolites) thrived and were subsequently silicified. Found within ancient sedimentary sequences.
Key Facts
- Hardness: 6.5-7 (Mohs scale)
- Specific Gravity: 2.58-2.64
- Crystal System: Trigonal (for quartz component)
- Color: Dark green to black with lighter green/black patterns.
- Luster: Dull to waxy, vitreous when polished.
- Transparency: Opaque.
- Fracture: Conchoidal.
- Cleavage: None.
- Composition: Primarily microcrystalline quartz (chert/chalcedony) with inclusions of various minerals such as arfvedsonite, aegirine, and feldspar, and fossilized cyanobacteria.
Quick Check
- Color: Dark green to black with lighter green/black orbicular patterns.
- Luster: Dull to waxy (unpolished), vitreous (polished).
- Streak: White.
Physical Characteristics
- Crystal Habit: Massive, cryptocrystalline aggregates.
- Cleavage Type: None.
- Fracture Type: Conchoidal.
- Tenacity: Brittle.
- Luster Type: Dull to waxy (unpolished), vitreous (polished).
Formation
Kambaba Jasper is not a true jasper in the geological sense, nor is it rhyolitic. It is a stromatolite, a fossilized microbial mat, primarily composed of chert (microcrystalline quartz) and often containing inclusions of various minerals like arfvedsonite, aegirine, and feldspar, which contribute to its distinctive patterns. These stromatolites formed in shallow marine environments through the trapping and binding of sedimentary grains by cyanobacteria and other microorganisms. Over geological time, these microbial mats were silicified, leading to the formation of chert, which is a cryptocrystalline variety of quartz. The characteristic orbicular or swirling patterns are a direct result of the layered growth of these ancient microbial communities. The green color is often attributed to inclusions of chlorite or other iron-bearing silicates.
Usage
Primarily used as an ornamental stone, for carvings, cabochons, beads, and decorative objects. It is also popular in metaphysical and New Age practices.
Age Distribution
Precambrian (specifically Neoarchean to Paleoproterozoic)
Where to Find
Madagascar
The primary and most well-known source of Kambaba Jasper, particularly from the Bongolava region.
South Africa
Similar stromatolitic cherts are found in ancient geological formations, though not always marketed as 'Kambaba Jasper'.
Finding Tips
Look for Distinctive Patterns
The most defining characteristic is the presence of fossilized stromatolitic structures, appearing as swirls, eyes, or concentric rings of varying shades of green and black.
Check Hardness
As it is primarily quartz, it should scratch glass (Mohs hardness 6.5-7).
Observe Luster
Unpolished surfaces will have a dull to waxy luster, while polished pieces will be vitreous.
Similar Rocks
Ocean Jasper
Orbicular Chalcedony/Jasper
Also known as: Orbicular Jasper
Rainforest Jasper
Rhyolitic Jasper
Also known as: Green Rhyolite
Mookaite Jasper
Radiolarian Chert
Also known as: Mookite
Scientific Classification
- Mineral Class
- Silicate (specifically Tectosilicate for quartz component)
- Group
- Quartz group (as chert/jasper is microcrystalline quartz)
- Crystal System
- Trigonal (for quartz component)
- Chemical Formula
- SiO2 (with various impurities and inclusions)
- Composition
- Silicon dioxide (SiO2) with trace elements and organic matter from fossilized microbial mats.
Explore Kambaba Jasper
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.