How to identify Blue Apatite in Quartz

To correctly identify Blue Apatite in Quartz (Apatite (Ca5(PO4)3(F,Cl,OH)) in Quartz (SiO2)), 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

   The specimen will exhibit blue inclusions or crystals (apatite) within a typically white, gray, or colorless matrix (quartz). The blue can range from light to dark, sometimes with a greenish tint.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Apatite typically has a vitreous to sub-resinous luster. Quartz has a vitreous luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be granular, massive, or crystalline. Apatite crystals may be prismatic or tabular within the quartz matrix.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Apatite often forms hexagonal prisms, sometimes with pyramidal terminations. Quartz typically forms hexagonal prisms with rhombohedral terminations, or can be anhedral (massive) when filling spaces.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Apatite has distinct basal cleavage {0001} and indistinct prismatic cleavage {1010}. Quartz has no cleavage, exhibiting conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in various igneous (e.g., pegmatites, granites), metamorphic (e.g., gneisses, schists, marbles), and hydrothermal vein deposits.

Key Facts

Hardness

Apatite: 5 (Mohs); Quartz: 7 (Mohs)

Specific Gravity

Apatite: 3.16-3.22; Quartz: 2.65

Crystal System

Apatite: Hexagonal; Quartz: Trigonal (often appears hexagonal)

Color

Apatite: Blue, green, yellow, brown, pink, purple, colorless; Quartz: Colorless, white, gray, purple, pink, brown, black (in this context, typically white/gray/colorless)

Luster

Apatite: Vitreous to sub-resinous; Quartz: Vitreous

Transparency

Apatite: Transparent to translucent; Quartz: Transparent to opaque

Fracture

Apatite: Conchoidal to uneven; Quartz: Conchoidal

Cleavage

Apatite: Distinct on {0001}, indistinct on {1010}; Quartz: None

Composition

Apatite: Calcium phosphate with fluoride, chloride, or hydroxide (Ca5(PO4)3(F,Cl,OH)); Quartz: Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Apatite: Prismatic, tabular, massive, granular; Quartz: Prismatic, massive, granular
• Cleavage Type: Apatite: Distinct basal {0001}, indistinct prismatic {1010}; Quartz: None
• Fracture Type: Apatite: Conchoidal to uneven; Quartz: Conchoidal
• Tenacity: Apatite: Brittle; Quartz: Brittle
• Luster Type: Apatite: Vitreous to sub-resinous; Quartz: Vitreous

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