sedimentary
Sandstone (Pet Rock)
Clastic sedimentary rock (primarily SiO2)
Hardness: 6-7 (Mohs); Color: Tan/Brown/Grey; Luster: Dull/Earthy; Structure: Granular/Clastic; Specific Gravity: 2.2-2.8. Note: Anthropomorphic facial features added with pigment/ink.
- Hardness
- 6-7 (Mohs)
- Color
- Tan/Brown/Grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Tan/Brown/Grey; Luster: Dull/Earthy; Structure: Granular/Clastic; Specific Gravity: 2.2-2.8. Note: Anthropomorphic facial features added with pigment/ink.
Formation & geological history
Formed through the accumulation and cementation of mineral particles (sand-sized grains), typically in riverbeds, deserts, or marine environments. The age varies by deposit location, ranging from recent to billions of years old.
Uses & applications
Used primarily as decorative art, novelty gifts, or paperweights. In unpainted form, sandstone is widely used in construction and landscaping.
Geological facts
This specimen is an example of a 'Pet Rock,' a 1970s cultural phenomenon. The markings are not geological but represent pareidolia—the human tendency to see faces in inanimate objects.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and visible sand grains. These are commonly found in arid regions, beach environments, and river basins worldwide.
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