How to identify Red Jasper

To correctly identify Red Jasper (Jasper (a variety of Chalcedony, SiO 2)), 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 opaque red, brick red, reddish-brown, or deep crimson. The color is generally uniform but can exhibit banding or mottling.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to vitreous (glassy) on fractured surfaces, often waxy to dull on unpolished surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Microgranular, dense, and fine-grained. Feels smooth to the touch.

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 to subconchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in association with volcanic rocks (e.g., rhyolite, basalt), hydrothermal veins, and as nodules or beds within sedimentary formations (e.g., shales, limestones). It can also occur in metamorphic terrains where silica-rich fluids have altered pre-existing rocks.

Key Facts

Hardness

6.5-7 on the Mohs scale

Specific Gravity

2.58-2.91

Crystal System

Trigonal (cryptocrystalline)

Color

Red, brick red, reddish-brown, deep crimson

Luster

Dull to vitreous (fracture), waxy to dull (unpolished)

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 to vitreous on fresh fracture, waxy to dull on surfaces.

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