Name: ______________________ SCORE: ____

Name: ______________________

REGENTS EARTH SCIENCE

Sedimentary Rock ID Lab

As you now know, rocks are composed of minerals or a combination of minerals. Rocks are

categorized into types based on the way in which they form. Sedimentary rocks form as weathered,

eroded and deposited materials are compacted and cemented together beneath the weight of

overlying sediments. Sedimentary rocks are classified into three major categories based on their

composition- CLASTIC, or fragmental (derived from weathering and erosion of land materials),

CRYSTALLINE (form from precipitation of dissolved salts in sea water) and BIOCLASTIC (fragments

of living organisms). The clastic sedimentary rocks are identified and named by grain size, while the

others are identified by composition. These characteristics, in turn, signify a particular environment

of formation. As you know from our study of igneous rocks, if you know the rock, you know the

past environment! Using your senses and the Scheme for Sedimentary Rock Identification, you

will be able to first classify and identify the rocks and their environments of formation.

PROCEDURE

First, take some time to familiarize yourself with the flow of the identification chart. The chart is read

by deciding on the texture first. The outline below may be helpful as a guide:

CLASTIC

(bits and pieces

of other rock)

CRYSTALLINE

(precipitated from

sea water)

Decision 2:

COMPOSITION

(what is it made of?)

Decision 2:

GRAIN SIZE

(gravel, sand, silt or

clay?)

BIOCLASTIC

(bits & pieces of

living organisms)

ROCK NAME

Decision 1:

TEXTURE

The texture and composition of sedimentary rocks are determined by the environment in which they

form. As you already know, sediments sort out by size, both vertically and horizontally. Horizontal

sorting is a major player in where sedimentary rocks form.

1. 2. 3. 4. 5. 6.

Highlands Shoreline Ocean