10 comprehensive state guides
Explore state geology United States geology by state
Connect statewide geologic history to regions, rocks, minerals, fossils, groundwater, hazards, and related named formations.
LithoMap field library
Geology, explained layer by layer.
Original, source-led guides for understanding the rocks beneath the map—and the specimens in your hand. Explore U.S. formations and state geology, then identify common rocks, minerals, and fossils through observable evidence.
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Resource collections
Start with the question you have
Formation profiles explain named bodies of rock through place and time. Identification guides begin with visible properties, simple tests, and close comparisons.
36 in-depth guides
Explore formations United States geologic formations
Compare distribution, age, depositional setting, rock types, fossils, minerals, field context, and authoritative sources.
24 identification guides
Identify rocks Rock identification
Use texture, grain size, structures, mineral composition, safe tests, and lookalike comparisons across the three rock families.
48 identification guides
Identify minerals Mineral identification
Compare hardness, streak, luster, cleavage, fracture, magnetism, geologic setting, and commonly confused minerals.
8 identification guides + legal overview
Explore fossils responsibly Fossil identification
Recognize common nonvertebrate and plant fossils, understand preservation and lookalikes, and check land-specific collecting rules before disturbing anything.
6 step-by-step methods
Learn field tests Rock and mineral field tests
Learn how to perform and interpret hardness, streak, breakage, acid reaction, magnetism, and specific-gravity tests without overstating the result.
59 vetted destinations · all 50 states
Explore every state Geology field trips
Plan rules-first rock, mineral, and non-dinosaur fossil visits, with authorized collecting clearly separated from observation-only protected sites.
Interactive field helper
Not sure where to begin?
Select observable properties such as texture, foliation, grain shape, hardness, streak, magnetism, cleavage, or acid response. The tool returns qualified possible matches and links to the complete guides.
Written for people. Structured for discovery.
Each guide uses direct answers, descriptive headings, consistent terminology, cited primary sources, and machine-readable page data. The wording is original; sources support the facts rather than supply the prose. Read our editorial standards and research method.