How to identify Mookaite Jasper

To correctly identify Mookaite Jasper (Siliceous rock (chert/chalcedony) with iron oxide inclusions), 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

   Varies widely, typically a mix of red, maroon, yellow, cream, white, and purple. Often exhibits distinct bands, swirls, or mottled patterns of these colors.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to waxy on unpolished surfaces; vitreous (glassy) to waxy when polished.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained, smooth to the touch. Can sometimes show faint sedimentary layering or brecciated textures.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Cryptocrystalline, meaning individual crystals are too small to be seen without magnification. Forms massive aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Jasper, being a microcrystalline quartz, lacks cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in weathered profiles of radiolarite beds, specifically within the Windalia Radiolarite formation. It forms through the silicification of porcelanite in a shallow marine or lacustrine setting, often associated with ancient hot springs or areas of high silica saturation.

Key Facts

Hardness

6.5 - 7 on the Mohs scale

Specific Gravity

2.58 - 2.91 g/cm³

Crystal System

Trigonal (cryptocrystalline aggregates)

Color

Red, maroon, yellow, cream, white, purple, often multi-colored and patterned.

Luster

Waxy to vitreous (polished), dull to waxy (unpolished).

Transparency

Opaque

Fracture

Conchoidal to sub-conchoidal

Cleavage

None

Composition

Silicon dioxide (SiO₂) with iron oxide (Fe₂O₃, FeO(OH)) inclusions.

Physical characteristics

• Crystal Habit: Massive, cryptocrystalline aggregates, often forming nodules or layers.
• Cleavage Type: None
• Fracture Type: Conchoidal to sub-conchoidal, typical of cryptocrystalline quartz.
• Tenacity: Brittle
• Luster Type: Waxy to vitreous

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