Where is Weathered Sedimentary Rock (with lichen/algae growth) found?
Sedimentary Rock (likely sandstone or siltstone) with lichen/algae growth
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Open the appWeathered Sedimentary Rock (with lichen/algae growth) occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Weathered Sedimentary Rock (with lichen/algae growth)
Global Terrestrial Environments
Found virtually anywhere sedimentary rocks are exposed to the atmosphere and have sufficient moisture for biological growth. This includes mountainous regions, coastal areas, deserts (in microclimates), forests, and urban environments.
Specific Examples
Common on sandstone cliffs in national parks (e.g., Zion, Bryce Canyon, Yosemite), siltstone exposures along river valleys, and any rock garden or old stone wall.
Collecting tips
- Look for Discoloration. Search for patches of green, gray, yellow, orange, or black on rock surfaces that contrast with the underlying rock color. These are often signs of lichen or algal growth.
- Observe Surface Texture. Note if the rock surface appears crumbly, pitted, or has a 'skin' of biological material. Lichens can be crusty or leafy, while algae might be slimy when wet.
- Consider the Environment. Biological weathering is more prevalent in humid or semi-humid environments, or on shaded rock faces where moisture persists. Look in areas with consistent moisture.
- Examine Rock Type. While any rock can weather, sandstones and siltstones are particularly susceptible due to their porosity and permeability, which allows water and biological agents to penetrate.
Quick Check
- Color:
- Variable, often mottled with greens, grays, yellows, oranges, blacks over the natural rock color.
- Luster:
- Dull to earthy, often obscured.
- Streak:
- Not applicable for the rock as a whole; individual mineral grains would have their own streak, and the biological growth does not produce a streak.
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