Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Brecciated Jasper is a distinctive form of jasper characterized by angular fragments of jasper cemented together by a fine-grained silica matrix, often stained by iron oxides. The fragments can vary in size and color, creating intricate patterns. The matrix material typically fills the voids and fractures, often contrasting in color with the jasper fragments. It is a microcrystalline quartz, meaning its individual crystals are too small to be seen without high magnification.
How to Identify
- Color
- Typically red, brown, or yellow fragments cemented by a matrix of similar or contrasting colors. The fragments often retain their original jasper coloration, while the matrix may be white, gray, or a different shade of red/brown due to iron oxide staining.
- Luster
- Dull to vitreous (glassy) on fractured surfaces.
- Texture
- Fragmental, with angular to sub-angular clasts (jasper fragments) embedded in a finer-grained matrix. The surface can be smooth when polished, but rough and uneven in its natural state.
- Crystal Form
- Cryptocrystalline (microcrystalline) quartz, meaning individual crystals are not visible to the naked eye. The overall form is massive or nodular, with distinct brecciated texture.
- Cleavage
- None, as it is a microcrystalline aggregate of quartz.
- Geological Environment
- Found in areas of tectonic activity (fault zones, shear zones), hydrothermal alteration zones, sedimentary basins where chert or jasper beds have been fractured and recemented, and sometimes in impact structures.
Key Facts
- Hardness: 6.5-7 on the Mohs scale (due to quartz content).
- Specific Gravity: 2.58-2.91 g/cm³ (varies with impurities).
- Crystal System: Trigonal (for the constituent quartz crystals, though the aggregate is massive).
- Color: Variable, typically reds, browns, yellows, and creams, often with contrasting matrix colors.
- Luster: Dull to vitreous.
- Transparency: Opaque.
- Fracture: Conchoidal to splintery.
- Cleavage: None.
- Composition: Silicon dioxide (SiO2) with significant iron oxide (Fe2O3, FeO(OH)) inclusions and other mineral impurities.
Quick Check
- Color: Red, brown, yellow fragments with contrasting or similar colored matrix.
- Luster: Dull to vitreous.
- Streak: White (for pure quartz), but may be reddish-brown if significant iron oxides are present and abraded.
Physical Characteristics
- Crystal Habit: Massive, cryptocrystalline aggregate with a brecciated texture.
- Cleavage Type: None.
- Fracture Type: Conchoidal to splintery.
- Tenacity: Brittle.
- Luster Type: Dull to vitreous.
Formation
Brecciated Jasper forms when existing jasper (a microcrystalline variety of quartz) is fractured and broken into angular fragments (breccia). These fragments are then naturally recemented by a silica-rich matrix, often containing iron oxides, which impart the characteristic red, brown, or yellow colors. The brecciation event can be caused by tectonic forces (faulting, folding), hydrothermal activity, impact events, or even sedimentary processes like slumping or collapse. The cementing material infiltrates the spaces between the fragments, binding them together. The iron oxides are typically responsible for the vibrant red, brown, and yellow hues, while the jasper fragments themselves can exhibit a range of colors.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, beads, carvings), and in decorative applications. Its attractive patterns and colors make it popular in jewelry and as a collectible mineral specimen.
Age Distribution
Ranges from Precambrian to Cenozoic, depending on the host rock and brecciation event.
Where to Find
Australia
Known for various types of jasper, including brecciated forms, particularly in Western Australia.
Brazil
Significant deposits of jasper and other cryptocrystalline quartz varieties.
United States
Found in several states, including Oregon, California, Idaho, and Arizona, often associated with volcanic or sedimentary formations.
South Africa
Known for various ornamental jaspers.
Russia
Ural Mountains region is a source of diverse jaspers.
Finding Tips
Look for fractured zones
Brecciated Jasper is often found in areas that have experienced geological stress, such as fault lines, shear zones, or areas of intense folding. Look for outcrops with evidence of fracturing and subsequent cementation.
Identify jasper outcrops
Since Brecciated Jasper is derived from existing jasper, identifying primary jasper deposits or beds is a good starting point. These are often found in sedimentary or volcanic environments.
Examine riverbeds and gravels
Water erosion can transport and concentrate durable rocks like jasper. Riverbeds, stream gravels, and alluvial deposits can be good places to find tumbled pieces of Brecciated Jasper.
Check for iron staining
The presence of red, brown, or yellow staining, indicative of iron oxides, can be a clue, as these often contribute to the matrix color in Brecciated Jasper.
Similar Rocks
Picture Jasper
Silicon dioxide (SiO2) with various mineral inclusions
Also known as: Landscape Jasper
Mookaite Jasper
Silicified radiolarite (SiO2)
Also known as: Mookite
Red Jasper
Silicon dioxide (SiO2) with hematite
Also known as: Bloodstone (when green with red spots)
Chert Breccia
Microcrystalline quartz (SiO2)
Also known as: Flint Breccia
Scientific Classification
- Mineral Class
- Silicate (specifically, Tectosilicate)
- Group
- Quartz Group (Cryptocrystalline variety)
- Crystal System
- Trigonal (for individual quartz crystals)
- Chemical Formula
- SiO2 (with Fe2O3, FeO(OH) as coloring agents)
- Composition
- Microcrystalline quartz with varying amounts of iron oxides (hematite, goethite, limonite) and other mineral inclusions.
Explore Brecciated Jasper
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.