GEL 1008: Lab 4 help

GEL 1008
PHYSICAL GEOLOGY

Physical Geology On-line Lab and Helpful Lab Hints

Exercise 4: Sedimentary Rocks

Sedimentary Rock Identification

Use the Table provided by me 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.