How to identify Blue Apatite

To correctly identify Blue Apatite (Apatite group (Fluorapatite, Chlorapatite, Hydroxylapatite)), 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 to deep blue, sometimes with greenish or violet undertones. Can also be colorless, yellow, green, brown, or pink, but 'Blue Apatite' specifically refers to the blue varieties.

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

   Smooth to slightly uneven on crystal faces.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal prismatic crystals, often with pyramidal terminations. Can also occur as massive, granular, or botryoidal aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor basal cleavage {0001}, often indistinct.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in igneous rocks (especially pegmatites, carbonatites, and alkaline igneous complexes), metamorphic rocks (marbles, gneisses, schists), and as detrital grains in sedimentary rocks. Gem-quality blue apatite is often found in pegmatites and hydrothermal veins.

Key Facts

Hardness

5 on the Mohs scale

Specific Gravity

3.16 - 3.22 (Fluorapatite), 3.17 - 3.23 (Chlorapatite), 3.15 - 3.20 (Hydroxylapatite)

Crystal System

Hexagonal

Color

Blue (sky blue, deep blue, greenish-blue, violet-blue)

Luster

Vitreous to sub-resinous

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Poor basal cleavage {0001}

Composition

Calcium phosphate with varying amounts of fluoride, chloride, or hydroxyl ions.

Physical characteristics

• Crystal Habit: Prismatic, tabular, massive, granular, botryoidal
• Cleavage Type: Poor, basal {0001}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Vitreous to sub-resinous

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