sedimentary
Mixed River Stones and Agates
Mixed Silicates and Ironstones (primarily SiO2 and Fe2O3)
Hardness: 6.5-7.0 (Mohs). Colors: Brown, dark grey, reddish-orange, and yellow. Luster: Dull, waxy, to sub-vitreous. Cleavage: None (conchoidal fracture). Texture: Water-worn, rounded to sub-angular.
- Hardness
- 6
- Luster
- Dull, waxy, to sub-vitreous
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Physical properties
Hardness: 6.5-7.0 (Mohs). Colors: Brown, dark grey, reddish-orange, and yellow. Luster: Dull, waxy, to sub-vitreous. Cleavage: None (conchoidal fracture). Texture: Water-worn, rounded to sub-angular.
Formation & geological history
Formed through secondary deposition in fluvial (river) environments. Many pieces are cryptocrystalline quartz (agate/jasper) or iron-rich sedimentary rocks that have been smoothed by water transport during the Holocene or Pleistocene.
Uses & applications
Primarily for lapidary use (tumbling), decorative landscaping, or as entry-level collection specimens.
Geological facts
The reddish-brown pieces likely contain Limonite or Hematite. The smoother, waxy stones are typical of alluvial agates which are hardy enough to survive long-distance river transport without shattering.
Field identification & locations
Identify in the field by looking for 'river polish'—naturally smoothed surfaces in streambeds. Agates can be identified by their translucency when held to light. Common in glacial till and active river basins.
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