How to identify Celestite Geode

To correctly identify Celestite Geode (Celestine (SrSO4) in a geode), 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 sky-blue, light blue, or colorless. Can also be white, gray, or rarely reddish-brown.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to pearly on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Crystals are typically well-formed, often tabular or prismatic, radiating inward from the geode walls. The outer shell is usually rougher, composed of the host rock.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system, commonly forming tabular or prismatic crystals. Often found as radiating aggregates or granular masses within geodes.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect cleavage in one direction ({001}), good in another ({210}), and distinct in a third ({100}). This results in blocky or tabular fragments.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Most commonly found in sedimentary rocks, particularly limestones, dolomites, and shales, often associated with evaporite deposits (gypsum, anhydrite) or hydrothermal alteration zones. They form in voids and vugs within these rocks.

Key Facts

Hardness

3-3.5 on the Mohs scale

Specific Gravity

3.95-3.97 (relatively heavy for a non-metallic mineral)

Crystal System

Orthorhombic

Color

Colorless, white, pale blue (most common), gray, reddish-brown

Luster

Vitreous to pearly

Transparency

Transparent to translucent

Fracture

Uneven to conchoidal

Cleavage

Perfect on {001}, good on {210}, distinct on {100}

Composition

Strontium sulfate (SrSO4)

Physical characteristics

• Crystal Habit: Tabular, prismatic, fibrous, granular, massive, radiating aggregates. Within geodes, often euhedral tabular or prismatic crystals growing inward.
• Cleavage Type: Perfect basal cleavage, good prismatic cleavage, distinct pinacoidal cleavage.
• Fracture Type: Uneven to conchoidal, brittle.
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) on crystal faces, pearly on cleavage surfaces.

Explore Celestite Geode