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Earth Science (PHSC 101) Virtual Laboratory Experiment # 4:
Fractionation of Detrital Rock Samples via Particle Size
Name: ________________________ Section: _______ Date: ______
Note on this virtual experiment
Read the introductory principle, procedure and experimental materials outlined below, and
understand as to how this virtual experiment would be conducted under real lab condition to
generate the data supplied in the Table below. After clearly understanding the procedure and
the formula for the calculations, enter calculated values in the blank columns and write brief
discussions as per the guideline, and resubmit the completed assignment in the Drop Box.
Introduction
Detrital sedimentary rocks are formed from sediments of weathered solid particles that vary in
size from 0.001 mm to about 256 mm, which consist of clay, silt, sand, pebbles, and boulders.
The composition of such loosely aggregated and mixed rocks could be determined by sieving
and passing the different size groups through different mesh-size sieves and weighing each
separate and determining the proportion % of fraction of the whole initial mass of the mixture.
The objective of this experiment is to fractionate detrital rock mixture sample. Initially weighed
mass of rock mixture sample is passed through stack of sieves with standard meshes or screen
size openings, ranging from 4 mm (mesh 5) to 0.025mm (mesh 60). The mass of each fraction
retained by each sieve (labeled as A, B, C, D from top to bottom) is determined and recorded in
in the appropriate on Table 1, Rep # 1. After data entered for Rep 1, all fractions are mixed
together, and the same procedure repeated again for Rep #2 and #3. The theoretical data
generated following the above procedure, and ready for calculation, is provided in Table 1. The
required experimental materials and detailed procedure is outlined below for your visualization.
Materials and Methods (see diagrams below)
Materials
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Detrital rock mixture samples
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Stackable Sieves:
# 1 (5 Mesh/inch; 4mm diameter)
# 2 (10 Mesh/inch; 2mm diameter)
# 3 (60 Mesh/inch; 0.250mm diameter)
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Analytical balance
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Weighing plastic saucers
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Sample collection trays
Detailed Step by Step Procedure
Replication 1 (Rep. #1)
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First, an empty plastic weighing saucer is tare on analytical balance and from the
supplied rock mixture about 650g is weighed and the exact weight is registered under 2nd
column (Whole sample mass). Then, the weighed rock mixture is transferred to the stack of
sieves arranged in size A, B, C, D (larger hole-size at the top and the collection pan at the
bottom). The cover is placed on the top sieve and the various fractions are separated by shaking
the stack of sieves for about 20 seconds. The fractions retained by each sieve are emptied on
previously tare plates, one at a time, starting from the top (fraction A) and the mass of each
fraction (A – D) is weighed in grams and recorded in the respective mass (g) columns of each
fraction, in Rep 1 row, on Table 1. After weighing, all the fractions are mixed on a sample
collection tray to carry out the same procedure as Rep. #2. The theoretical data is already
provided for you to work on.
Replication 2 (Rep. #2)
The exact procedure outline for Rep. #1 above is repeated on the whole sample which is
obtained by mixing the fractions at the end of procedure on Rep #1. But the data obtained on
whole sample mass as well as the mass of the fractions from the sieving (A, B, C, D), is entered
in the appropriate columns for Rep #2.
Replication 3 (Rep. #3)
The exact procedure outline for Rep. #1 and Rep. #2 above is repeated on the whole sample
which is obtained by mixing the fractions at the end of procedure on Rep #2. But the data
obtained on whole sample mass as well as the mass of the fractions from the sieving (A, B, C, D),
is entered in the appropriate columns for Rep #3.
Assignment
•
From the theoretical raw data given on n the three replications on Table 1 for Whole
Sample Mass and the Mass of the different fraction (A, B, C, D), calculate the percentage (%) of
the mass of each fraction (A, B, C, D) of the whole mass, and enter values in the % column, for
each replication. Also calculate the mean and total mass and % values and enter them in the
blank space provided in the respective columns and rows.
•
Plot Excel bar-graph showing the mean mass (g) and percentage (%) distribution of the
different detrital rock size fractions. Put the rock fraction (A, B, C, and D) on the x-axis, and the
mean mass (g) and percentage (%) on the y-axis. Draw the graph on excel and paste on or attach
to the document..
Table 1: Theoretical mass data for whole sample and different fractions of detrital rock sample
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