How to identify Chlorite Quartz

To correctly identify Chlorite Quartz (SiO2 with (Mg,Fe)3(Si,Al)4O10(OH)2), 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

   Green, ranging from pale to dark, often mottled or patterned due to chlorite distribution. The quartz itself is typically colorless or milky.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) for the quartz, dull to pearly for the chlorite inclusions.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly rough depending on the surface finish and density of chlorite inclusions. Can appear fibrous or granular internally.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz typically forms hexagonal prisms with pyramidal terminations. Chlorite inclusions can be massive, disseminated, or form distinct pseudo-hexagonal or tabular crystals within the quartz.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz: None. Chlorite: Perfect basal cleavage (one direction). This is usually not observable in included chlorite unless the chlorite is a large, distinct crystal.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphic rocks (schists, gneisses, phyllites), hydrothermal veins, and altered igneous rocks (e.g., altered basalts, gabbros, granites).

Key Facts

Hardness

Quartz: 7 on Mohs scale. Chlorite: 2-2.5 on Mohs scale. The overall hardness of the aggregate will be dominated by quartz.

Specific Gravity

Quartz: 2.65 g/cm³. Chlorite: 2.6-3.3 g/cm³. The aggregate's specific gravity will be slightly higher than pure quartz if chlorite content is significant.

Crystal System

Quartz: Trigonal. Chlorite: Monoclinic.

Color

Colorless to milky white (quartz) with green inclusions (chlorite).

Luster

Vitreous (quartz), dull to pearly (chlorite).

Transparency

Transparent to translucent (quartz), opaque (chlorite inclusions).

Fracture

Conchoidal (quartz).

Cleavage

Quartz: None. Chlorite: Perfect basal cleavage (one direction).

Composition

Silicon dioxide (SiO2) for quartz, and a complex hydrous magnesium iron aluminum silicate ((Mg,Fe)3(Si,Al)4O10(OH)2) for chlorite.

Physical characteristics

• Crystal Habit: Quartz: Prismatic, massive, granular. Chlorite: Micaceous, tabular, fibrous, massive, disseminated.
• Cleavage Type: Quartz: None. Chlorite: Perfect in one direction {001}.
• Fracture Type: Conchoidal (quartz).
• Tenacity: Brittle (quartz), flexible but inelastic (chlorite).
• Luster Type: Vitreous (quartz), dull to pearly (chlorite).

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