igneous
Granite River Pebble
Granite
Hardness: 6–7 Mohs; Color: Gray, pinkish-tan, and black speckles with brown iron staining; Luster: Dull/Matte (worn) to vitreous (minerals); Structure: Phaneritic (coarse-grained) crystalline; Specific gravity: 2.63–2.75
- Hardness
- 6–7 Mohs
- Luster
- Dull/Matte (worn) to vitreous (minerals)
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6–7 Mohs; Color: Gray, pinkish-tan, and black speckles with brown iron staining; Luster: Dull/Matte (worn) to vitreous (minerals); Structure: Phaneritic (coarse-grained) crystalline; Specific gravity: 2.63–2.75
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen was later eroded and tumbled in a high-energy water environment, such as a river or beach, during the Holocene era.
Uses & applications
Used primarily as decorative landscaping stone, drainage gravel, or as a pocket stone for collectors. In larger forms, granite is used in construction and countertops.
Geological facts
The brown markings on the surface are likely iron oxide 'rust' staining caused by the weathering of iron-bearing minerals like biotite or magnetite within the rock.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and smooth, rounded water-worn shape. Commonly found in riverbeds, glacial till, and coastal areas near crystalline bedrock.
