1. LEQ: What characteristics are used to classify and identify sedimentary rock?
Key Terms: clast, clastic rock, biochemical/organic rock, chemical rock

2. Classifying Sedimentary Rock Review
Geologists classify sedimentary rock according to the type of sediment that make up the rock.
Clastic Sedimentary Rock
Sediment type: Rock fragments
Organic (Biochemical) Sedimentary Rock
Sediment type: Organic material
Chemical Sedimentary Rock
Sediment type: dissolved mineral crystallization.

3. Clastic Sedimentary Rock
Most sedimentary rocks are in this group.
Form when rock fragments (clasts) are compacted and cemented together.
Clasts vary in size.
Clastic sedimentary rocks are grouped by the size of the clasts that make up the rock.
Clasts (rock fragments) in a clastic sedimentary rock are also observe for their
Grain shape
How well the grains are sorted.

4. Sediment Grain Size Scale
Gravel
Sand
Silt
Clay

5. Clastic Sedimentary Rock Sediment Size Chart (The Wentworth Scale)

6. Grain Shape
Grain shape is observed as angular or rounded, and is described as indicated in the examples below.

7. Grain Sorting
How well sorted the clasts are sorted is also observed as indicated in the examples below.

8. Common Clastic Sedimentary Rocks Sediment Size: Gravel
Conglomerate:
rounded grain well sorted
Breccia:
angular grain poorly sorted

9. Common Clastic Sedimentary Rocks Sediment Size: Sand
Sandstone

10. Common Clastic Sedimentary Rocks Sediment Size: Silt, Clay, Mud
Shale or Mudstone

11. Organic Sedimentary Rock
Also known as biological or biochemical sedimentary rocks.
Form when organic material (remains of plants or animals) are compacted and cemented together.
Organic sedimentary rocks are identified by the type of organic material that makes up the rock.

12. Organic Sedimentary Rocks: Sediment: Plant Remains
Coal Peat
Both contain an abundance of Carbon

13. Organic Sedimentary Rocks: Sediment: Animal Remains
Limestone Chalk
Both contain an abundance of Calcium Carbonate
Calcium Carbonate reacts with Hydrochloric Acid (fizz test)

14. Chemical Sedimentary Rock
Also known as evaporites.
Form from the crystallization of dissolved minerals in a solution.
The liquid (water) evaporates
Dissolved minerals crystallize as the water evaporates.
Identified by the mineral that crystallizes.

15. Chemical Sedimentary Rocks
Rock Salt Rock Gypsum Crystallized Limestone