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Red Jasper with Hematite is a microcrystalline variety of quartz (chalcedony) that is opaque and typically exhibits a vibrant red to reddish-brown color due to the presence of finely disseminated hematite (iron oxide). The hematite can be uniformly distributed, giving a solid red appearance, or it can form distinct patterns, streaks, or inclusions within the jasper matrix. It is a hard and durable material, making it suitable for polishing.
How to Identify
- Color
- Typically opaque red, reddish-brown, or brick-red, often with darker red or metallic gray streaks or patches where hematite concentration is higher. The red color is due to hematite (Fe2O3).
- Luster
- Dull to vitreous (glassy) on fractured surfaces; waxy to sub-vitreous when polished.
- Texture
- Smooth, dense, and fine-grained. Can feel slightly gritty if the hematite is more granular or if it's a less pure form.
- Crystal Form
- Massive, cryptocrystalline (microscopic crystals). Does not exhibit macroscopic crystal forms.
- Cleavage
- None. Exhibits conchoidal fracture.
- Geological Environment
- Found in sedimentary environments, often associated with ancient seafloors where iron-rich sediments and silica precipitated. Also occurs in hydrothermal veins, volcanic rocks, and as secondary mineralization in weathered iron-rich deposits. Commonly found in Banded Iron Formations (BIFs).
Key Facts
- Hardness: 6.5 - 7 on the Mohs scale (due to quartz/jasper component).
- Specific Gravity: 2.58 - 2.91 (varies with hematite content; pure jasper is ~2.65, hematite is 5.26).
- Crystal System: Trigonal (for quartz/jasper component); Hexagonal (for hematite component).
- Color: Red, reddish-brown, brick-red, due to hematite inclusions.
- Luster: Dull, waxy, or sub-vitreous.
- Transparency: Opaque.
- Fracture: Conchoidal to splintery.
- Cleavage: None.
- Composition: Silicon dioxide (SiO2) with iron oxide (Fe2O3) inclusions.
Quick Check
- Color: Opaque red to reddish-brown, sometimes with darker streaks or metallic flecks.
- Luster: Dull to waxy/sub-vitreous.
- Streak: Reddish-brown (for jasper) to cherry-red or reddish-brown (for hematite). A pure hematite streak is typically reddish-brown.
Physical Characteristics
- Crystal Habit: Massive, cryptocrystalline aggregates.
- Cleavage Type: None.
- Fracture Type: Conchoidal to splintery.
- Tenacity: Brittle.
- Luster Type: Dull, waxy, sub-vitreous.
Formation
Red Jasper with Hematite forms primarily through the precipitation of silica (forming jasper) in iron-rich environments. The iron oxides, predominantly hematite (Fe2O3), are responsible for the characteristic red coloration. This can occur in various settings: 1. Hydrothermal alteration of iron-rich rocks. 2. Diagenesis of iron-rich sediments, often associated with Banded Iron Formations (BIFs) where microcrystalline quartz (chert/jasper) interbeds with iron oxides. 3. Weathering and oxidation of iron-bearing minerals, leading to the deposition of iron-rich silica gels that later lithify. The hematite can be disseminated throughout the jasper matrix or occur as distinct veins, bands, or inclusions.
Usage
Primarily used as an ornamental stone, in lapidary arts for cabochons, beads, and carvings. Also collected by mineral enthusiasts. Historically, red ochre (a form of hematite-rich clay) was used as a pigment.
Age Distribution
Ranges from Precambrian to Cenozoic, depending on the specific geological formation.
Where to Find
Western Australia
Known for significant deposits of Banded Iron Formations (BIFs) which often contain jasper and hematite, particularly in the Pilbara region.
United States (Oregon, California, Idaho)
Various localities produce red jasper, often with hematite inclusions or banding, from volcanic and sedimentary contexts.
India
A historical source of various jaspers, including red varieties with iron oxide content.
Brazil
Known for diverse mineral deposits, including some occurrences of jasper and hematite.
South Africa
Significant BIFs and associated iron ore deposits, which can include jasper-hematite formations.
Finding Tips
Look for Iron-Rich Sedimentary Environments
Explore areas with ancient marine sedimentary rocks, especially those associated with iron ore deposits or Banded Iron Formations. Riverbeds and gravel pits in such regions can also yield tumbled specimens.
Identify Red Coloration and Opacity
Search for opaque, dense rocks with a distinct red to reddish-brown color. The presence of metallic gray streaks or a slightly metallic sheen can indicate higher hematite content.
Test Hardness
Jasper is hard (Mohs 6.5-7). It will scratch glass and steel. This helps differentiate it from softer red rocks or clays.
Observe Fracture
Freshly broken surfaces should exhibit a conchoidal (shell-like) fracture, characteristic of quartz varieties.
Similar Rocks
Red Chert
SiO2 (with iron oxides)
Also known as: Radiolarian Chert (if biogenic)
Ironstone
Various iron-rich minerals (e.g., FeCO3, FeO(OH))
Also known as: Siderite, Limonite, Goethite-rich rock
Jaspilite
SiO2 (Jasper) and Fe2O3 (Hematite/Magnetite)
Also known as: Banded Iron Formation (BIF)
Carnelian
SiO2 (with iron oxides, typically less opaque than jasper)
Also known as: Cornelian
Scientific Classification
- Mineral Class
- Silicate (Jasper) and Oxide (Hematite)
- Group
- Quartz Group (Jasper) and Hematite Group (Hematite)
- Crystal System
- Trigonal (Jasper) and Hexagonal (Hematite)
- Chemical Formula
- SiO2 (Jasper) + Fe2O3 (Hematite)
- Composition
- Microcrystalline quartz (chalcedony) with varying amounts of hematite (iron oxide) as the primary coloring agent.
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