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Quartz with Chlorite is a variety of quartz (silicon dioxide) that contains inclusions of chlorite group minerals. The chlorite inclusions impart a green color to the quartz, ranging from pale green to dark forest green, and can appear as wisps, clouds, phantoms, or distinct crystals within the quartz matrix. The transparency of the quartz can vary from clear to translucent or opaque, depending on the density and distribution of the chlorite.
How to Identify
- Color
- Green, ranging from pale to dark, often mottled or patterned due to chlorite distribution. The quartz itself is typically colorless or milky.
- Luster
- Vitreous (glassy) for the quartz, dull to pearly for the chlorite inclusions.
- Texture
- Smooth to slightly rough depending on the surface finish and density of chlorite inclusions. Can appear fibrous or granular internally.
- Crystal Form
- 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.
- Cleavage
- Quartz: None. Chlorite: Perfect basal cleavage (one direction). This is usually not observable in included chlorite unless the chlorite is a large, distinct crystal.
- Geological Environment
- 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.
Quick Check
- Color: Green (due to chlorite inclusions) within a colorless or milky quartz matrix.
- Luster: Vitreous (glassy) for quartz, dull to pearly for chlorite.
- Streak: White (for quartz), pale green to greenish-white (for chlorite, if a pure chlorite sample could be streaked).
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).
Formation
Quartz with Chlorite forms under a range of metamorphic conditions (greenschist to amphibolite facies) and hydrothermal alteration processes. Chlorite typically forms from the alteration of mafic minerals (e.g., pyroxenes, amphiboles, biotite) in the presence of water, often during retrograde metamorphism or hydrothermal fluid circulation. Quartz, being a ubiquitous mineral, crystallizes alongside or encapsulates these chlorite inclusions. The chlorite can be disseminated throughout the quartz, form distinct phantoms, or create fibrous inclusions.
Usage
Primarily a collector's mineral and used in lapidary arts for cabochons, carvings, and ornamental objects due to its aesthetic appeal. It has no significant industrial uses beyond its constituent minerals.
Age Distribution
Found in rocks of various ages, from Precambrian to Cenozoic, depending on the metamorphic or hydrothermal events that formed it.
Where to Find
Brazil
Known for producing high-quality chlorite included quartz, often with distinct phantom formations.
Himalayan Region (e.g., Pakistan, Nepal)
Source of clear quartz with fine, often fibrous, chlorite inclusions, sometimes forming 'lodolite' or 'garden' quartz.
United States (e.g., Arkansas, North Carolina)
Various localities yield quartz with chlorite, particularly in metamorphic terrains.
Alps (e.g., Switzerland, Austria)
Classic localities for well-formed quartz crystals, some of which contain chlorite inclusions.
Finding Tips
Look in Metamorphic Terrains
Focus on areas with greenschist to amphibolite facies metamorphic rocks, especially those derived from mafic or ultramafic protoliths.
Hydrothermal Veins
Explore quartz veins cutting through altered igneous or metamorphic rocks, as these are common sites for chlorite formation.
Examine Quartz Crystals Closely
Chlorite inclusions can be subtle. Look for green coloration, wisps, or cloudy areas within otherwise clear quartz crystals.
Check Mine Dumps and Road Cuts
These disturbed areas often expose fresh rock faces where mineral occurrences are more easily spotted.
Similar Rocks
Prasiolite
SiO2 (heat-treated amethyst or naturally occurring green quartz)
Also known as: Green Amethyst
Aventurine
SiO2 with Fuchsite (chromium mica) or other mica inclusions
Also known as: Green Aventurine
Epidote Quartz
SiO2 with Ca2(Al,Fe)3(SiO4)3(OH) inclusions
Also known as: Epidote Included Quartz
Seraphinite
(Mg,Fe)5Al(Si3Al)O10(OH)8 (a specific chlorite variety)
Also known as: Clinochlore
Scientific Classification
- Mineral Class
- Quartz: Tectosilicate. Chlorite: Phyllosilicate (sheet silicate).
- Group
- Quartz Group, Chlorite Group
- Crystal System
- Quartz: Trigonal. Chlorite: Monoclinic.
- Chemical Formula
- SiO2 (Quartz) with (Mg,Fe)3(Si,Al)4O10(OH)2 (Chlorite, general formula)
- Composition
- Silicon dioxide with hydrous magnesium iron aluminum silicate inclusions.
Explore Chlorite Quartz
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