How to identify Red Jasper

To correctly identify Red Jasper (Jasper (a variety of Chalcedony, SiO2)), 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

   Opaque red to reddish-brown, often uniform but can be mottled or banded. The red is due to hematite inclusions.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to vitreous, sometimes waxy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly granular, very fine-grained, opaque.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, cryptocrystalline aggregates; individual crystals are microscopic and not visible to the naked eye.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in association with volcanic rocks, hydrothermal veins, sedimentary deposits (e.g., banded iron formations, chert beds), and as infillings in fissures and cavities in various rock types.

Key Facts

Hardness

6.5-7 on Mohs scale

Specific Gravity

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

Crystal System

Trigonal (cryptocrystalline aggregates)

Color

Red, reddish-brown (due to hematite inclusions)

Luster

Dull, vitreous, waxy

Transparency

Opaque

Fracture

Conchoidal to subconchoidal

Cleavage

None

Composition

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

Physical characteristics

• Crystal Habit: Massive, nodular, botryoidal, or as vein fillings; cryptocrystalline aggregates.
• Cleavage Type: None
• Fracture Type: Conchoidal to subconchoidal, splintery in some varieties.
• Tenacity: Brittle
• Luster Type: Dull, vitreous, waxy

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