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This is a mineral assemblage characterized by the presence of scheelite, quartz, and pyrite. Scheelite, a calcium tungstate, is the economically significant component, often appearing as translucent to opaque, white, yellow, or brownish crystals. Quartz, silicon dioxide, is typically present as transparent to translucent, colorless to white, anhedral to euhedral crystals, forming the bulk of the vein material. Pyrite, iron disulfide, is easily recognizable by its metallic luster and brassy yellow color, often forming cubic or pyritohedral crystals. The association of these three minerals is indicative of specific hydrothermal ore-forming processes, particularly those related to tungsten mineralization.
How to Identify
- Color
- Scheelite: White, yellow, yellowish-brown, greenish-yellow, or colorless. Quartz: Colorless, white, or various hues depending on impurities. Pyrite: Pale brass-yellow, often tarnishing to iridescent colors.
- Luster
- Scheelite: Vitreous to adamantine. Quartz: Vitreous. Pyrite: Metallic.
- Texture
- Scheelite: Often granular, massive, or as distinct bipyramidal crystals. Quartz: Crystalline, massive, or granular. Pyrite: Crystalline (cubes, pyritohedrons, octahedrons), massive, or disseminated.
- Crystal Form
- Scheelite: Tetragonal bipyramidal crystals, often pseudo-octahedral; also massive or granular. Quartz: Hexagonal prisms with pyramidal terminations; massive. Pyrite: Cubic, pyritohedral, or octahedral crystals; also massive or granular.
- Cleavage
- Scheelite: Distinct on {101} and {112}. Quartz: None (conchoidal fracture). Pyrite: Indistinct on {001} and {110}.
- Geological Environment
- High-temperature hydrothermal veins, skarns, greisen deposits, and contact metamorphic zones associated with granitic intrusions.
Key Facts
- Hardness: Scheelite: 4.5-5 Mohs; Quartz: 7 Mohs; Pyrite: 6-6.5 Mohs
- Specific Gravity: Scheelite: 5.9-6.1; Quartz: 2.65; Pyrite: 4.95-5.10
- Crystal System: Scheelite: Tetragonal; Quartz: Trigonal; Pyrite: Isometric
- Color: Scheelite: White, yellow, brownish; Quartz: Colorless, white; Pyrite: Brassy yellow
- Luster: Scheelite: Vitreous to adamantine; Quartz: Vitreous; Pyrite: Metallic
- Transparency: Scheelite: Transparent to translucent; Quartz: Transparent to translucent; Pyrite: Opaque
- Fracture: Scheelite: Uneven to subconchoidal; Quartz: Conchoidal; Pyrite: Uneven to conchoidal
- Cleavage: Scheelite: Distinct on {101} and {112}; Quartz: None; Pyrite: Indistinct on {001} and {110}
- Composition: Scheelite: Calcium tungstate (CaWO4); Quartz: Silicon dioxide (SiO2); Pyrite: Iron disulfide (FeS2)
Quick Check
- Color: Scheelite: White to yellow; Quartz: Colorless to white; Pyrite: Brassy yellow
- Luster: Scheelite: Vitreous to adamantine; Quartz: Vitreous; Pyrite: Metallic
- Streak: Scheelite: White; Quartz: White; Pyrite: Greenish-black to brownish-black
Physical Characteristics
- Crystal Habit: Scheelite: Bipyramidal, massive, granular; Quartz: Prismatic, massive, granular; Pyrite: Cubic, pyritohedral, massive
- Cleavage Type: Scheelite: Distinct; Quartz: None; Pyrite: Indistinct
- Fracture Type: Scheelite: Uneven to subconchoidal; Quartz: Conchoidal; Pyrite: Uneven to conchoidal
- Tenacity: Scheelite: Brittle; Quartz: Brittle; Pyrite: Brittle
- Luster Type: Scheelite: Vitreous to adamantine; Quartz: Vitreous; Pyrite: Metallic
Formation
This assemblage typically forms in high-temperature hydrothermal veins, skarns, and greisen deposits. Scheelite precipitates from tungsten-rich fluids, often associated with granitic intrusions. Quartz is a common gangue mineral in these environments, and pyrite forms under reducing conditions, often co-precipitating with other sulfides and oxides.
Usage
Scheelite is the primary ore mineral for tungsten, a critical metal used in high-strength alloys, filaments, and cutting tools. Quartz is used in various industrial applications, including glass manufacturing, electronics, and abrasives. Pyrite is a minor source of sulfur and iron, but its primary significance in this assemblage is as an indicator mineral for hydrothermal activity and potential ore deposits.
Age Distribution
Varies widely depending on the geological setting, from Precambrian to Cenozoic.
Where to Find
China
Major producer of tungsten, with significant scheelite deposits found in various provinces, often associated with quartz veins and sulfide mineralization.
South Korea
Historically significant scheelite deposits, such as the Sangdong mine, known for high-grade scheelite-quartz-pyrite veins.
United States
California (Pine Creek Mine), Nevada, and Colorado have notable scheelite occurrences, often in skarn and hydrothermal vein deposits.
Canada
Yukon Territory and British Columbia host scheelite-bearing skarns and hydrothermal veins.
Australia
Tasmania and New South Wales have scheelite deposits, sometimes in association with quartz and sulfides.
Portugal
Historically important tungsten mining region, with scheelite found in quartz veins.
Finding Tips
UV Light Detection
Scheelite is famously fluorescent under shortwave ultraviolet (SWUV) light, typically emitting a bright blue to yellowish-white glow. This is a primary identification tool in the field.
Associated Minerals
Look for this assemblage in areas known for granitic intrusions, skarns, or greisen deposits. Other associated minerals might include fluorite, arsenopyrite, chalcopyrite, and various silicates.
Specific Gravity Test
Scheelite has a relatively high specific gravity (5.9-6.1), which can help distinguish it from lighter gangue minerals like quartz.
Hardness Test
Scheelite (4.5-5 Mohs) is softer than quartz (7 Mohs) but harder than many other common gangue minerals. Pyrite (6-6.5 Mohs) is harder than scheelite.
Geological Context
Focus exploration efforts in areas with known tungsten mineralization or geological settings conducive to its formation, such as contact metamorphic aureoles around granites.
Similar Rocks
Wolframite with Quartz
(Fe,Mn)WO4 (Wolframite), SiO2 (Quartz)
Also known as: Tungsten Ore
Cassiterite with Quartz and Pyrite
SnO2 (Cassiterite), SiO2 (Quartz), FeS2 (Pyrite)
Also known as: Tin Ore
Molybdenite with Quartz
MoS2 (Molybdenite), SiO2 (Quartz)
Also known as: Molybdenum Ore
Scientific Classification
- Mineral Class
- Scheelite: Tungstates; Quartz: Silicates (Tectosilicates); Pyrite: Sulfides
- Group
- Scheelite: Scheelite Group; Quartz: Quartz Group; Pyrite: Pyrite Group
- Crystal System
- Scheelite: Tetragonal; Quartz: Trigonal; Pyrite: Isometric
- Chemical Formula
- CaWO4 (Scheelite), SiO2 (Quartz), FeS2 (Pyrite)
- Composition
- Scheelite: Calcium, Tungsten, Oxygen; Quartz: Silicon, Oxygen; Pyrite: Iron, Sulfur
Explore Scheelite with Quartz and Pyrite
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