Description and Identification of Soils (Visual-Manual Procedure) - Soil Properties: Testing, Measurement, and Evaluation - page 28

Identification of Peat
(1) A sample composed primarily of vegetable tissue in various
stages of decomposition that has a fibrous to amorphous texture,
usually a dark brown to black color, and an organic odor shall be
designated as a highly organic soil and shall be identified as peat,
PT, and not subjected to the identification procedures described
hereafter.
Preparation for Identification
(1) The soil identification portion of this practice is based on the
portion of the soil sample that will pass a 3-in. (75-mm) sieve. The
larger than 3-in. (75-mm) particles must be removed manually, for
a loose sample, or mentally, for an intact sample before classifying
the soil.
(2) Estimate and note the percentage of cobbles and the percent-
age of boulders. Performed visually, these estimates will be on the
basis of volume percentage.
Note 4 —Since the percentages of the particle-size distribution
in ASTM Test Method D 2487 are by dry weight, and the esti-
mates of percentages of gravel, sand, and fines in this practice
are by dry weight, it is recommended that the report state that
the percentages of cobbles and boulders are by volume.
(3) Of the fraction of the soil smaller than 3 in. (75 mm), estimate
and note the percentage, by dry weight, of the gravel, sand, and
fines (see suggested procedures at the end of the chapter).
Note 5 —Since the particle-size components appear visually on
the basis of volume, considerable experience is required to esti-
mate the percentages on the basis of dry weight. Frequent com-
parison with laboratory particle-size analyses should be made.
(3.1) The percentages shall be estimated to the closest 5%. The per-
centages of gravel, sand, and fines must add up to 100%.
(3.2) If one of the components is present but not in sufficient
quantity to be considered 5% of the smaller than 3-in. (75-mm)
portion, indicate its presence by the term trace, for example, trace
of fines. A trace is not to be considered in the total of 100% for the
components.
Preliminary Identification
(1) The soil is fine grained if it contains 50% or more fines. Follow
the procedures for identifying fine-grained soils.
(2) The soil is coarse grained if it contains less than 50% fines.
Follow the procedures for identifying coarse-grained soils.