How to identify Blue Apatite

To correctly identify Blue Apatite (Apatite group (Ca5(PO4)3(F,Cl,OH))), 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 from light blue to deep, vibrant blue, sometimes with a greenish tint. The color can be unevenly distributed.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to sub-resinous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically smooth on crystal faces, granular in massive forms.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal prismatic crystals are common, often with pyramidal terminations. Can also be massive, granular, or botryoidal.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor to indistinct on {0001} and {1010}. Often exhibits conchoidal fracture rather than distinct cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in igneous rocks (e.g., pegmatites, carbonatites, alkaline igneous rocks), metamorphic rocks (e.g., marbles, schists, gneisses), and sedimentary rocks (e.g., phosphorite deposits). Also occurs in hydrothermal veins.

Key Facts

Hardness

5 on the Mohs scale

Specific Gravity

3.1-3.2

Crystal System

Hexagonal

Color

Blue, green, yellow, brown, violet, pink, colorless (blue is specific to Blue Apatite)

Luster

Vitreous to sub-resinous

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Poor to indistinct on {0001} and {1010}

Composition

Calcium phosphate with varying amounts of fluoride, chloride, and hydroxyl ions

Physical characteristics

• Crystal Habit: Hexagonal prismatic crystals, often with pyramidal terminations; also massive, granular, columnar, or botryoidal.
• Cleavage Type: Poor to indistinct basal {0001} and prismatic {1010}. Often fractures rather than cleaves cleanly.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Vitreous (glassy) to sub-resinous.

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