Quartz Arenite
Quartz arenite is a sandstone composed of more than about 90 to 95 percent quartz, depending on the classification used, in well-sorted, rounded grains. It is the 'cleanest' and most mature sandstone, the end product of repeated weathering and reworking.
Quartz arenite is a sandstone composed of more than about 90 to 95 percent quartz, depending on the classification used, in well-sorted, rounded grains. It is the "cleanest" and most mature sandstone, the end product of repeated weathering and reworking.
🪨 Geology Guide Specimen: Open Quartz Arenite in the CRV Science Rock & Mineral ID Guide to log the specimen, compare it with the other 6 subgroups of Sedimentary, and test your eye in LithoClade.
Maturity: Why Is It So Rich in Quartz?
Quartz resists weathering, while feldspar, mica and rock fragments break down to clay. Sand that is recycled many times, or carried far, loses everything but quartz, and its grains become rounded and sorted. Such "supermature" sandstone usually has little clay and is cemented with silica or calcite.
Dunes and Beaches: Where Does It Form?
Quartz arenites often record wind-blown dunes or wave-washed beach and shelf sands. Sweeping cross-bedding preserves the slip faces of ancient dunes, as in the Navajo Sandstone of the Colorado Plateau, a Jurassic desert, and grains rolled by wind often have frosted surfaces.
Resources: Why Do Quartz Arenites Matter?
Quartz Arenite at a Glance
| Property | Value |
|---|---|
| Type / variety | Supermature Silica-Cemented Quartz Sandstone |
| Composition | >90–95% Well-Rounded Detrital Quartz Grains (0.0625–2 mm) + Silica/Calcite Cement |
| Geology Guide group | Sedimentary Rocks (Clastic, Chemical & Biogenic) |
| Rock Classification | Medium Clastic (Sandstones) |
| Mohs hardness | Mohs 6.5–7 |
| Texture / habit | Well-sorted, frosted or rounded medium grains (0.1–1 mm) |
| Density | 2.55–2.65 g/cm³ |
| Lustre and cleavage | Sugary gritty surface, often displaying sweeping cross-bedding |
| Geological setting | Desert erg dunes (e.g., Navajo/Zion) and wave-washed shallow marine shelves |
| Diagnostic feature (Geology Guide) | Clean, well-sorted buff-to-reddish gritty rock composed of over 90% rounded, frosted quartz grains (0.1–1 mm) arranged in sweeping wind-blown or wave-washed cross-beds. |
| Quartz content | Above about 90-95% |
| Typical settings | Dunes, beaches and shallow-marine shelves |
See Also
- Arkose — a feldspar-rich sandstone
- Greywacke — a muddy, immature sandstone
- Silicate Weathering — the process that removes everything but quartz