How to identify Aragonite

To correctly identify Aragonite (Aragonite), 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, or gray, but can also be yellow, green, blue, violet, brown, or pink due to impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to resinous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Often fibrous, columnar, or radiating aggregates. Individual crystals can be prismatic or acicular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system. Commonly forms pseudohexagonal twins, radiating aggregates, stalactitic, columnar, or fibrous masses. Acicular (needle-like) crystals are characteristic.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Distinct cleavage in one direction ({010}), and imperfect in two others ({110} and {011}). This is often difficult to observe in fine-grained or fibrous aggregates.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in evaporitic deposits, hot spring deposits (tufa), speleothems (cave formations), mollusk shells, coral skeletons, serpentinites, and as a secondary mineral in altered igneous and metamorphic rocks. Also forms in high-pressure, low-temperature metamorphic facies (e.g., blueschist facies).

Key Facts

Hardness

3.5 - 4 on the Mohs scale

Specific Gravity

2.93 - 2.95 g/cm³

Crystal System

Orthorhombic

Color

White, colorless, gray, yellow, green, blue, violet, brown, pink

Luster

Vitreous to resinous

Transparency

Transparent to translucent

Fracture

Subconchoidal to uneven

Cleavage

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

Composition

Calcium Carbonate (CaCO3)

Physical characteristics

• Crystal Habit: Acicular, prismatic, columnar, fibrous, radiating, stalactitic, massive. Often forms pseudohexagonal twins.
• Cleavage Type: Distinct in one direction ({010}), imperfect in two others ({110} and {011}).
• Fracture Type: Subconchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Vitreous (glassy) to resinous.

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