How to identify Red Jasper with Epidote

To correctly identify Red Jasper with Epidote (SiO2 (Jasper) with Ca2(Al,Fe)3(SiO4)3(OH) (Epidote)), 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

   Dominantly red (jasper) with distinct pistachio-green, yellowish-green, or olive-green patches, streaks, or veins (epidote).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Jasper: Dull to vitreous. Epidote: Vitreous to resinous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Jasper: Smooth, microgranular, often conchoidal fracture surfaces. Epidote: Granular, prismatic, or massive, often with a slightly rougher feel than jasper.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Jasper: Cryptocrystalline, massive. Epidote: Typically anhedral to subhedral grains, sometimes prismatic crystals in vugs or veins.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Jasper: None (conchoidal fracture). Epidote: Perfect on {001}, good on {100}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Often found in metamorphic terrains, particularly where mafic or calcareous rocks have undergone regional or contact metamorphism, and where silica-rich fluids were present. Can be associated with hydrothermal alteration zones.

Key Facts

Hardness

Jasper: 6.5-7 (Mohs). Epidote: 6-7 (Mohs).

Specific Gravity

Jasper: 2.58-2.91. Epidote: 3.35-3.47.

Crystal System

Jasper: Trigonal (cryptocrystalline). Epidote: Monoclinic.

Color

Red (jasper) and pistachio-green to yellowish-green (epidote).

Luster

Jasper: Dull to vitreous. Epidote: Vitreous to resinous.

Transparency

Opaque (both components).

Fracture

Jasper: Conchoidal. Epidote: Uneven to subconchoidal.

Cleavage

Jasper: None. Epidote: Perfect on {001}, good on {100}.

Composition

Jasper: Silicon dioxide (SiO2) with iron oxide impurities. Epidote: Calcium aluminum iron sorosilicate hydroxide (Ca2(Al,Fe)3(SiO4)3(OH)).

Physical characteristics

• Crystal Habit: Jasper: Massive, cryptocrystalline. Epidote: Prismatic, granular, massive, fibrous.
• Cleavage Type: Jasper: Absent. Epidote: Perfect basal {001}, good {100}.
• Fracture Type: Jasper: Conchoidal. Epidote: Uneven to subconchoidal.
• Tenacity: Brittle (both components).
• Luster Type: Jasper: Dull to vitreous. Epidote: Vitreous to resinous.

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