Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Brecciated Jasper is a distinctive variety of jasper characterized by angular fragments of jasper cemented together by a fine-grained siliceous matrix. The fragments are typically red, brown, or yellow, while the matrix can be white, gray, black, or a contrasting shade of red or brown, creating a striking mosaic-like appearance. It is a form of chalcedony, which is a cryptocrystalline variety of quartz, meaning its crystals are too small to be seen without high magnification.
How to Identify
- Color
- Dominantly red, brown, or yellow angular fragments, often with white, gray, black, or contrasting red/brown matrix. The colors are due to iron oxide inclusions.
- Luster
- Dull to vitreous (glassy) on fractured surfaces, typically dull to waxy on polished surfaces.
- Texture
- Brecciated texture, characterized by sharp, angular fragments embedded in a finer-grained matrix. The fragments are typically opaque.
- Crystal Form
- Cryptocrystalline (microscopic crystals), massive, anhedral. Individual crystals are not visible to the naked eye.
- Cleavage
- None, due to its cryptocrystalline nature.
- Geological Environment
- Found in areas of significant tectonic activity, hydrothermal alteration zones, sedimentary basins where collapse breccias form, or impact structures. It is often associated with volcanic rocks, chert beds, and other siliceous deposits.
Key Facts
- Hardness: 6.5-7 on the Mohs scale.
- Specific Gravity: 2.58-2.91 g/cm³.
- Crystal System: Trigonal (for quartz, the constituent mineral).
- Color: Variable, typically red, brown, yellow fragments with white, gray, black, or contrasting matrix.
- Luster: Dull to waxy.
- Transparency: Opaque.
- Fracture: Conchoidal to splintery.
- Cleavage: None.
- Composition: Silicon dioxide (SiO2) with various iron oxide inclusions and other impurities.
Quick Check
- Color: Angular fragments of red, brown, yellow jasper cemented by a contrasting matrix.
- Luster: Dull to waxy.
- Streak: White.
Physical Characteristics
- Crystal Habit: Massive, cryptocrystalline aggregates.
- Cleavage Type: None.
- Fracture Type: Conchoidal to splintery.
- Tenacity: Brittle.
- Luster Type: Dull to waxy.
Formation
Brecciated Jasper forms when existing jasper (a cryptocrystalline variety of quartz, SiO2) is fractured or broken into angular fragments (breccia) and subsequently recemented by a siliceous matrix, often containing iron oxides or other minerals that impart color. This brecciation can occur due to tectonic activity (faulting, folding), hydrothermal alteration, impact events, or sedimentary processes (e.g., collapse breccias). The cementing material is typically chalcedony or quartz, often stained red, brown, or yellow by iron oxides, which highlights the angular fragments.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, spheres, carvings), and in jewelry. Its attractive patterns and durability make it popular for decorative items. It is also collected by mineral enthusiasts.
Age Distribution
Globally distributed, found in formations ranging from Precambrian to Cenozoic, depending on the specific geological events that caused brecciation.
Where to Find
Australia
Known for various types of jasper, including brecciated forms, particularly in Western Australia.
Brazil
Significant deposits of chalcedony and jasper varieties, including brecciated forms.
United States
Found in several states, including Oregon, Idaho, and California, often in association with volcanic activity or sedimentary chert beds.
Madagascar
Produces a wide range of ornamental jaspers, some of which exhibit brecciated textures.
South Africa
Known for various jasper types, including those with brecciated structures.
Finding Tips
Look for Tectonic Zones
Areas with historical or active faulting, folding, or other tectonic disturbances are prime locations for breccia formation.
Examine Hydrothermal Alteration Zones
Jasper can be formed or altered by hydrothermal fluids, and these areas can also lead to brecciation and subsequent cementation.
Check Sedimentary Deposits
Look in chert beds, ancient riverbeds, or areas where collapse breccias might have formed.
Identify Characteristic Patterns
The angular fragments and contrasting matrix are key visual identifiers. Look for sharp, broken pieces cemented together.
Test Hardness
Jasper is relatively hard (Mohs 6.5-7), so it will scratch glass and will not be easily scratched by a steel knife.
Similar Rocks
Picture Jasper
Jasper (variety of Chalcedony)
Also known as: Landscape Jasper
Mookaite Jasper
Radiolarite (a variety of Chalcedony)
Also known as: Mook Jasper
Orbicular Jasper
Jasper (variety of Chalcedony)
Also known as: Ocean Jasper
Scientific Classification
- Mineral Class
- Silicates (Tectosilicates)
- Group
- Quartz Group (Chalcedony variety)
- Crystal System
- Trigonal
- Chemical Formula
- SiO2 (with impurities)
- Composition
- Silicon dioxide with varying amounts of iron oxides (hematite, goethite, limonite) and other mineral inclusions that impart color and pattern.
Explore Brecciated Jasper
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.