How to identify Aragonite

To correctly identify Aragonite (Aragonite (variety 'Spudnik' or 'Moroccan')), 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 white, colorless, light brown, yellow, green, or blue. The 'Spudnik' variety is often white to cream.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to resinous, sometimes greasy on fracture surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   The 'Spudnik' variety exhibits a distinctive radiating, acicular (needle-like) crystal texture, often forming botryoidal or globular aggregates.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system. Commonly forms prismatic, acicular, or tabular crystals. Twinning is common, often forming pseudohexagonal prisms. The 'Spudnik' variety is characterized by radiating aggregates of acicular crystals.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Distinct cleavage in one direction ({010}), imperfect in two others ({110} and {011}). Often difficult to observe due to fine-grained or acicular habit.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in various environments including hot springs (tufa, travertine), caves (speleothems), hydrothermal veins, marine and freshwater sediments, and as a component of mollusk shells and corals. The 'Spudnik' variety is often found in cave systems or specific hydrothermal deposits.

Key Facts

Hardness

3.5 - 4 on the Mohs scale.

Specific Gravity

2.93 - 2.95 (higher than calcite, which is 2.71). This is a key distinguishing feature.

Crystal System

Orthorhombic.

Color

White, colorless, light brown, yellow, green, blue.

Luster

Vitreous to resinous.

Transparency

Transparent to translucent to opaque.

Fracture

Subconchoidal to uneven.

Cleavage

Distinct on {010}, imperfect on {110} and {011}.

Composition

Calcium Carbonate (CaCO3).

Physical characteristics

• Crystal Habit: Prismatic, acicular, tabular, columnar, fibrous, stalactitic, pisolitic, oolitic, botryoidal. Often twinned, forming pseudohexagonal prisms. 'Spudnik' variety is radiating acicular aggregates.
• Cleavage Type: Distinct in one direction ({010}), imperfect in two others ({110} and {011}).
• Fracture Type: Subconchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Vitreous to resinous.

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