How to identify Red Jasper

To correctly identify Red Jasper (SiO2 (microcrystalline quartz)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically brick red, deep red, reddish-brown, or sometimes mottled with other colors. The red is due to hematite inclusions.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to sub-vitreous (waxy) on unpolished surfaces; vitreous to resinous when polished.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained, dense, and opaque. Smooth to the touch when polished.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, cryptocrystalline (individual crystals are too small to be seen without high magnification). Does not form macroscopic crystals.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Exhibits conchoidal to splintery fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in association with volcanic rocks, hydrothermal alteration zones, sedimentary chert beds (especially those formed in deep marine environments), and as infillings in various rock types. Often occurs in nodules, veins, or as bedded deposits.

Key Facts

Hardness

6.5-7 on the Mohs scale

Specific Gravity

2.58-2.91 g/cm³ (typically around 2.65 g/cm³)

Crystal System

Trigonal (due to its microcrystalline quartz composition)

Color

Red, reddish-brown, brick red (due to hematite inclusions)

Luster

Dull, waxy, or sub-vitreous; vitreous when polished

Transparency

Opaque

Fracture

Conchoidal to splintery

Cleavage

None

Composition

Silicon dioxide (SiO2) with iron oxide (hematite) inclusions

Physical characteristics

• Crystal Habit: Massive, cryptocrystalline aggregates; does not form macroscopic crystals.
• Cleavage Type: None
• Fracture Type: Conchoidal to splintery
• Tenacity: Brittle
• Luster Type: Dull, waxy, sub-vitreous

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