Physical Geology Helpful Lab Hints
Exercise 4: Sedimentary Rock Identification
Sedimentary Rock Identification
Use the Table provided by me at the beginning of the semester (or on this web site) to identify the rocks and their characteristics.
Step 1: Determine if the rock is detrital or chemical/biochemical.
| Characterisitics | Detrital (clastic) | Chemical/Biochemical (non-clastic) |
| gravel, sand, silt | mostly | little or none |
| clay or mud | some (clay mud) | some (calcite mud is found in some limestones) |
| fossils | usually very few | may have many |
| feel | gritty, dirty | most are not gritty/dirty |
| crystalline | none | common, may be microscopic |
Step 2
- If the rock is detrital, use Table 4.4 at the top of page 66. The primary characteristic to observe is the size of the sediment grains in the rock.
- If the rock is chemical or biochemical, use Table 4.5 at the bottom of page 66. The primary characteristic to observe is the mineral and chemical composition of the rock. To recognize the minerals present, use the characteristics in Table 4.3 on page 65.