Chalcopyrite with Quartz

Mineral assemblage

CuFeS2 (Chalcopyrite) and SiO2 (Quartz)

Also known as: Copper Pyrites in Quartz, Fool's Gold in Quartz (misnomer for chalcopyrite)

Got a photo? Identify rocks instantly with the Rockby app

Description

Chalcopyrite with Quartz refers to an assemblage where the copper-iron sulfide mineral chalcopyrite (CuFeS2) is found in association with the silicate mineral quartz (SiO2). This combination is extremely common in many types of copper ore deposits worldwide. Chalcopyrite typically appears as brassy yellow, metallic grains or crystals, often tarnishing to iridescent blues, purples, and reds. Quartz, in contrast, is usually colorless, white, or smoky, with a vitreous luster, and forms distinct crystals or massive aggregates. The two minerals can be intimately intergrown, with chalcopyrite disseminated within quartz veins or forming distinct crystals on or within quartz matrices.

How to Identify

Color: Chalcopyrite: Brassy yellow, often tarnishing to iridescent blue, purple, red, or green. Quartz: Colorless, white, milky, smoky, purple (amethyst), yellow (citrine), pink (rose quartz).
Luster: Chalcopyrite: Metallic. Quartz: Vitreous (glassy) to greasy.
Texture: Chalcopyrite: Granular, massive, sometimes crystalline. Quartz: Crystalline (euhedral to anhedral), massive, granular.
Crystal Form: Chalcopyrite: Tetragonal, often forming pseudotetrahedral or disphenoidal crystals, but more commonly massive or disseminated grains. Quartz: Hexagonal, forming prismatic crystals with pyramidal terminations, or massive.
Cleavage: Chalcopyrite: Poor, indistinct. Quartz: None (conchoidal fracture).
Geological Environment: Hydrothermal veins, porphyry copper deposits, skarns, volcanogenic massive sulfide (VMS) deposits, and other ore-forming environments where copper mineralization occurs in silica-rich fluids.

Key Facts

Hardness: Chalcopyrite: 3.5-4 (Mohs). Quartz: 7 (Mohs).
Specific Gravity: Chalcopyrite: 4.1-4.3. Quartz: 2.65.
Crystal System: Chalcopyrite: Tetragonal. Quartz: Trigonal (often described as hexagonal).
Color: Chalcopyrite: Brassy yellow, often tarnished iridescent. Quartz: Colorless, white, milky, smoky, various other colors.
Luster: Chalcopyrite: Metallic. Quartz: Vitreous to greasy.
Transparency: Chalcopyrite: Opaque. Quartz: Transparent to translucent.
Fracture: Chalcopyrite: Uneven to conchoidal. Quartz: Conchoidal.
Cleavage: Chalcopyrite: Poor, indistinct {011}. Quartz: None.
Composition: Chalcopyrite: Copper iron sulfide (CuFeS2). Quartz: Silicon dioxide (SiO2).

Quick Check

Color: Brassy yellow (chalcopyrite) with colorless/white/smoky (quartz)
Luster: Metallic (chalcopyrite) and Vitreous (quartz)
Streak: Greenish-black (chalcopyrite) and White (quartz)

Physical Characteristics

Crystal Habit: Chalcopyrite: Massive, disseminated grains, rarely distinct pseudotetrahedral crystals. Quartz: Prismatic crystals, massive, granular.
Cleavage Type: Chalcopyrite: Poor, indistinct. Quartz: Absent.
Fracture Type: Chalcopyrite: Uneven to conchoidal. Quartz: Conchoidal.
Tenacity: Chalcopyrite: Brittle. Quartz: Brittle.
Luster Type: Chalcopyrite: Metallic. Quartz: Vitreous to greasy.

Formation

Chalcopyrite and Quartz commonly form together in a variety of hydrothermal environments, including porphyry copper deposits, skarn deposits, volcanogenic massive sulfide (VMS) deposits, and epithermal veins. Quartz often acts as a gangue mineral, filling fractures and cavities alongside the ore-forming chalcopyrite. The formation involves the precipitation of these minerals from hot, aqueous solutions circulating through crustal rocks. The presence of quartz indicates silica-rich fluids, which are common in many ore-forming systems.

Usage

Chalcopyrite is the most important ore mineral of copper, accounting for the vast majority of global copper production. Quartz, while not directly used for its copper content, is a common gangue mineral that must be separated during ore processing. Industrially, quartz itself is used in glass manufacturing, ceramics, abrasives, and as a raw material for silicon production. Specimens with well-formed chalcopyrite crystals in a quartz matrix are also valued by mineral collectors.

Age Distribution

Found in geological formations ranging from Precambrian to Cenozoic, depending on the specific ore deposit type.

Where to Find

Bingham Canyon Mine, Utah, USA

One of the largest open-pit mines in the world, a classic porphyry copper deposit with abundant chalcopyrite and quartz.

Chuquicamata Mine, Chile

Another massive porphyry copper deposit, known for its extensive chalcopyrite mineralization within quartz veins.

Butte, Montana, USA

Historically significant copper mining district with numerous hydrothermal veins containing chalcopyrite and quartz.

Kidd Creek Mine, Ontario, Canada

A world-class VMS deposit where chalcopyrite is a primary ore mineral, often associated with quartz.

Cornwall, England, UK

Historic mining region known for tin and copper deposits, with chalcopyrite and quartz common in lode systems.

Finding Tips

Look for Metallic Luster

Chalcopyrite's distinctive brassy yellow metallic luster, often with iridescent tarnish, will stand out against the vitreous luster of quartz.

Check for Crystal Habits

While chalcopyrite often occurs as massive grains, look for its characteristic pseudotetrahedral crystals. Quartz will typically show hexagonal prisms or massive forms.

Consider Geological Context

Chalcopyrite with quartz is indicative of hydrothermal mineralization. Search in areas known for copper deposits, especially those associated with igneous intrusions or volcanic activity.

Perform a Streak Test

Chalcopyrite has a greenish-black streak, which helps distinguish it from pyrite (greenish-black to brownish-black) and gold (golden yellow). Quartz has a white streak.

Hardness Test

Chalcopyrite is relatively soft (3.5-4 on Mohs scale) compared to quartz (7). This difference can be used to differentiate them if they are not clearly distinct.

Similar Rocks

Pyrite with Quartz

FeS2 (Pyrite) and SiO2 (Quartz)

Also known as: Iron Pyrites in Quartz, Fool's Gold in Quartz

Bornite with Quartz

Cu5FeS4 (Bornite) and SiO2 (Quartz)

Also known as: Peacock Ore in Quartz

Gold in Quartz

Au (Gold) and SiO2 (Quartz)

Also known as: Auriferous Quartz

Scientific Classification

Mineral Class: Chalcopyrite: Sulfide. Quartz: Silicate (Tectosilicate).
Group: Chalcopyrite: Sulfide minerals. Quartz: Quartz group.
Crystal System: Chalcopyrite: Tetragonal. Quartz: Trigonal.
Chemical Formula: CuFeS2 (Chalcopyrite) and SiO2 (Quartz)
Composition: Chalcopyrite: Copper (34.6%), Iron (30.4%), Sulfur (35.0%). Quartz: Silicon (46.7%), Oxygen (53.3%).

Explore Chalcopyrite with Quartz

Identification Localities & Collecting Look-alikes

Identify rocks anywhere

Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.

Download on theApp Store Get it onGoogle Play Continue onWeb

Open in app