metamorphic or igneous
Riverstone (Quartzite/Granite Cobble)
Silicon Dioxide (SiO2) based Quartzite or Silicate-rich Granite
Hardness: 6-7 on Mohs scale; Color: Gray, tan, or brown with dirty surface; Luster: Dull (weathered) to vitreous (on fresh break); Crystal Structure: Granular or microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, tan, or brown with dirty surface
- Luster
- Dull (weathered) to vitreous (on fresh break)
Identified More metamorphic or igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Gray, tan, or brown with dirty surface; Luster: Dull (weathered) to vitreous (on fresh break); Crystal Structure: Granular or microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the recrystallization of sandstone (quartzite) or cooling magma (granite). Its rounded, smooth elliptical shape is the result of long-term fluvial erosion in rivers or glacial transport during the Pleistocene to Holocene epochs.
Uses & applications
Used primarily in landscaping, concrete aggregate, road construction, and decorative garden features. High-quality smooth stones are sometimes used in hot stone massage or as painting surfaces for crafts.
Geological facts
Rocks like this are often called 'clasts' by geologists. Their roundness is a direct indicator of the distance they have traveled; the smoother and rounder the stone, the longer it has been tumbled by water or ice.
Field identification & locations
Identify in the field by its smooth, egg-like texture and high hardness (it will scratch glass). Commonly found in stream beds, alluvial fans, and glacial till. Collectors look for unique colors or perfectly symmetrical oval shapes.
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![Quartz with Muscovite Mica (Silicon Dioxide (SiO2) with Potassium aluminum silicate hydroxide fluoride [KAl2(AlSi3O10)(F,OH)2]) — mineral](https://media.rock.id/0c7649cd-4e3b-497f-9306-feae39b499ce-thumbnail.jpg)
Quartz with Muscovite Mica
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mineral