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Quartzite with Gold is a metamorphic rock composed predominantly of quartz (SiO2), typically greater than 90%, that contains visible native gold (Au) inclusions. The quartzite itself is characterized by its hard, non-foliated to weakly foliated texture, where original quartz grains have recrystallized and interlocked, forming a very durable rock. The gold within the quartzite can appear as disseminated specks, flakes, wires, or small nuggets, often associated with quartz veins or sulfide minerals (e.g., pyrite, arsenopyrite) that may also be present within the quartzite matrix or cross-cutting structures. The gold content can vary significantly, from trace amounts to economically viable concentrations.
How to Identify
- Color
- Quartzite: typically white, gray, pink, or reddish, depending on impurities. Gold: metallic yellow to brassy yellow.
- Luster
- Quartzite: vitreous to greasy. Gold: metallic, bright.
- Texture
- Quartzite: Granoblastic, interlocking quartz grains, often sugary or glassy. Gold: visible as metallic specks, flakes, or wires within the quartzite matrix.
- Crystal Form
- Quartzite: Anhedral, interlocking quartz grains. Gold: typically anhedral masses, flakes, wires, or dendritic forms; rarely euhedral crystals (octahedra, dodecahedra).
- Cleavage
- Quartzite: None (quartz has no cleavage). Gold: None.
- Geological Environment
- Metamorphic terrains, often associated with ancient cratons, greenstone belts, or orogenic belts where hydrothermal fluids have introduced gold into pre-existing quartzites or their protoliths.
Key Facts
- Hardness: Quartzite: 7 on Mohs scale. Gold: 2.5-3 on Mohs scale.
- Specific Gravity: Quartzite: 2.65 g/cm³. Gold: 19.3 g/cm³ (pure gold), but can vary with impurities (e.g., electrum is 12-15 g/cm³).
- Crystal System: Quartzite (quartz): Trigonal. Gold: Isometric.
- Color: Quartzite: white, gray, pink, red. Gold: golden yellow.
- Luster: Quartzite: vitreous to greasy. Gold: metallic.
- Transparency: Quartzite: translucent to opaque. Gold: opaque.
- Fracture: Quartzite: conchoidal to subconchoidal. Gold: hackly.
- Cleavage: Quartzite: none. Gold: none.
- Composition: Quartzite: primarily SiO2. Gold: Au (native element).
Quick Check
- Color: Quartzite: variable (white, gray, pink); Gold: metallic yellow.
- Luster: Quartzite: vitreous; Gold: metallic.
- Streak: Quartzite: white; Gold: metallic yellow.
Physical Characteristics
- Crystal Habit: Quartzite: Granular, massive. Gold: Dendritic, arborescent, wire-like, flaky, massive, rarely octahedral or dodecahedral.
- Cleavage Type: Quartzite: None. Gold: None.
- Fracture Type: Quartzite: Conchoidal to subconchoidal. Gold: Hackly.
- Tenacity: Quartzite: Brittle. Gold: Malleable and ductile.
- Luster Type: Quartzite: Vitreous to greasy. Gold: Metallic.
Formation
Quartzite forms from the metamorphism of quartz-rich sandstone. Gold mineralization in quartzite typically occurs through hydrothermal processes where gold-bearing fluids circulate through fractures, veins, or disseminated pores within the quartzite, depositing native gold. This can happen during or after the metamorphic event.
Usage
Primarily as an ore for gold extraction. High-grade specimens are also sought after by mineral collectors.
Age Distribution
Precambrian to Cenozoic, depending on the age of the protolith sandstone and the subsequent metamorphic event and gold mineralization.
Where to Find
Witwatersrand Basin, South Africa
World's largest gold deposit, primarily hosted in auriferous conglomerates, but also in associated quartzites and other metasedimentary rocks.
Mother Lode, California, USA
Gold is found in quartz veins within metamorphosed sedimentary and igneous rocks, including quartzites.
Abitibi Greenstone Belt, Canada
Numerous gold deposits, often associated with quartz veins cutting through metamorphosed volcanic and sedimentary rocks, including quartzites.
Yilgarn Craton, Western Australia
Major gold-producing region with deposits in various host rocks, including quartzites and banded iron formations.
Finding Tips
Look for Quartzite Outcrops
Identify areas with known quartzite formations. Quartzite is very resistant to weathering and often forms prominent ridges or hills.
Examine Quartz Veins and Fractures
Gold is frequently concentrated in quartz veins that cut through the quartzite. Look for these veins, especially where they show signs of alteration or sulfide mineralization.
Pan for Gold in Associated Streams
If gold is present in the quartzite, erosion may release it into nearby streams. Panning in stream sediments downstream from quartzite outcrops can indicate the presence of gold.
Use a Loupe or Hand Lens
Gold particles can be very small. A magnification tool is essential for identifying fine specks of gold within the rock matrix.
Check for Associated Minerals
Gold often co-occurs with sulfide minerals like pyrite ('fool's gold'), arsenopyrite, and galena. The presence of these minerals can be an indicator of potential gold mineralization.
Similar Rocks
Gold-bearing Quartz Vein
Quartz (mineral) with native gold (Au)
Also known as: Auriferous Quartz
Conglomerate with Gold
Conglomerate (sedimentary rock) with native gold (Au)
Also known as: Auriferous Conglomerate, Gold Conglomerate
Schist with Gold
Schist (metamorphic rock) with native gold (Au)
Also known as: Auriferous Schist, Gold Schist
Scientific Classification
- Mineral Class
- Quartz: Silicate (Tectosilicate). Gold: Native Element.
- Group
- Quartz: Quartz Group. Gold: Gold Group.
- Crystal System
- Quartz: Trigonal. Gold: Isometric.
- Chemical Formula
- Quartz: SiO2. Gold: Au.
- Composition
- Quartzite: Silicon dioxide. Gold: Pure gold, often with minor silver (Ag) and other trace elements.
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