U.S. GEOLOGICAL SURVEY CIRCULAR 1071 

Separation and Identification 

of the Silt-Sized Heavy-Mineral 

Fraction in Sediments 
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Separation and Identification 

of the Silt-Sized Heavy-Mineral 

Fraction in Sediments 

By JUDITH A. COMMEAU, LAWRENCE j. POPPE, and 

ROBERT F. COMMEAU 

U.S. GEOLOGICAL SURVEY CIRCULAR 1071 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 

Free on application to 

Book and Open-File Report Sales 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Commeau, judith A. 

Separation and identification of the silt-sized heavy-mineral fraction in sediments I by judith A. Commeau, Lawrence j. Poppe, and Robert F. Commeau. 

p. em. - (U.S. Geological Survey circular : 1071) 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.412: 1971 

1. Heavy minerals-Analysis. 2. Sediments (Geology)-Analysis. 

3. Image processing. 4. X-ray diffractometer. I. Poppe, Lawrence j. 

II. Commeau, F. R. Ill. Title. IV. Series 

QE471.2.C64 1992 

549'.1-dc20 91-29574 

CIP 
CONTENTS 

Abstract 1 

Introduction 1 

Methods 1 

Sample Preparation 1 

Size Fractionation and Heavy-Mineral Separation 1 

Preparation of Samples for Analysis 3 

Sample Analysis-Particle Size, Shape, and Chemistry 3 

Test Study Area-Results and Discussion 7 

Summary 12 

References Cited 13 

FIGURES 

1. Flow diagram outlining separation procedures 2 

2. Plot of density versus concentration of sodium polytungstate 2 

3. Schematic of SEMI AIAIEDS system 4 

4. Flow diagram of procedures performed during SEM/AIAIEDS analysis 5 

5. Map of sample locations in test study area 7 

6-10. Examples of actual data output from the image analysis program for a sample 

collected from station N5 in the test study area (fig. 5): 

6. Histogram of particle population percent versus chemical class (macro 

class) 10 

7. The number of particles in user-specified size ranges within each chemical 

category 10 

8. The percentage of total particles in size ranges for each chemical 

category 11 

9. Histogram of weight percentages versus chemical category 11 

10. Weight percentages for size ranges 12 

TABLES 

1. Partial list of user-defined chemical categories 6 

2. List of chemical categories or macro classes 6 

3. Results from a test sample, particles mounted versus identified 7 

4. Weight percentages of silt-sized minerals from test area 8 

5. Abundances of nonmicaceous, silt-sized heavy minerals in samples from test study 

area 9 

Contents Ill 

Separation and Identification of the 

Silt-Sized Heavy-Mineral Fraction in Sediments 

By Judith A. Commeau, Lawrence J. Poppe, and Robert F. Commeau 

Abstract 

The separation of silt-sized minerals by specific gravity is made possible by using a nontoxic, heavy liquid 

medium of sodium polytungstate and water. Once separated, the silt-sized heavy-mineral fraction is prepared for 

analysis with a scanning electron microscope equipped 

with an automatic image analyzer and energy-dispersive 

spectrometer. Particles within each sample are sized and 

sorted according to their chemistry, and the data are 

tabulated in histograms and tables. Where possible, the 

user can define the chemical categories to simulate distinct mineral groups. Polymorphs and minerals that have 

overlapping compositions are combined into a group and 

differentiated by X-ray diffraction. Hundreds of particles 

can be rapidly sized and classified by chemistry. The 

technique can be employed on sediments from any environment. 

INTRODUCTION 

Analyses of the heavy-mineral fraction of sediments 

provide information on the provenance, depositional environment, and resource potential of the areas sampled. At 

present, heavy-mineral analyses are conducted on the sand 

fraction because of the difficulties encountered in suspending or wetting silt-sized material in organic heavy liquids 

and in identifying the mineralogy of this size fraction by 

petrographic microscope. However, most of the heavy 

minerals occur in the finer fractions because of their greater 

specific gravity (>2.85). In addition, sediments from most 

low-energy depositional environments contain little or no 

sand-sized heavy minerals from which to obtain statistically 

significant petrographic data. 

The recent introduction of a new heavy liquid 

medium, an aqueous solution of sodium polytungstate 

[3Na2W04 ·9W03 ·H20] (SPT) (Callahan, 1987; Gregory 

and Johnston, 1987), and the use of a scanning electron 

microscope (SEM) equipped with an energy-dispersive 

X-ray spectrometer (EDS) and an automatic image analyzer 

(AlA) enable us to examine the grain size, chemistry, and 

Manuscript approved for publication July 25, 1991. 

mineralogy of the silt-sized heavy-mineral fraction of sediments. The SPT solution is nontoxic, readily adjustable in 

density from 1.0 to 3.1 g/cm3

, reusable, and, in the absence 

of calcium ions, chemically inert. It is also an ideal 

substitute for the carcinogenic halogenated lower alkanes 

such as tetrabromoethane and bromoform. The SEM/EDS/ AlA equipment allows us to automatically determine the 

size and shape of hundreds of particles at a time and 

categorize them by chemistry. 

The samples analyzed to demonstrate the procedures 

presented in this report were collected during the Atlantic 

Margin Program (Emery, 1966), an extensive study of the 

geological, biological, and hydrological characteristics of 

the Continental Shelf, slope, and rise of the Eastern United 

States. These surficial-sediment grab samples were selected 

because data on grain size, mineralogy, and chemistry of 

the sand fraction have been compiled (Ross, 1970; Hathaway, 1971). The analysis of the silt-sized fraction from 

these samples would complement these data and allow us to 

identify trends between the two size fractions. 

METHODS 

Sample Preparation 

Size Fractionation and Heavy-Mineral Separation 

The silt-sized particles must be isolated from the 

coarser and finer fractions before the heavy-mineral separation is performed (fig. 1). The sand fraction is separated 

by wet-sieving the samples through a 62-J.Lm (ASTM 

number 230) sieve and is reserved for sand-fraction heavymineral analyses. The clays less than 4 J.Lm in average 

diameter are removed from the fine fraction by decantation 

(Folk, 1974) and may be reserved for identification by 

X-ray powder diffraction. The decantation procedure 

involves settling the sample twice in a 0.5 percent sodium 

metaphosphate solution to de-flocculate the particulates and 

at least five additional times in distilled water. The samples 

are shaken and ultrasonified between each decantation to 

ensure that the sample is completely disaggregated. Decantation also serves to remove most of the free cations that 

Methods 
ISOLATE 

AND 

FILTER 

HEAVY 

FRACTION 

SEMI 

AIA!EDS 

X-RAY 

ANALYSIS 

SILT-SIZE 

MATERIAL REMAINS 

(0.062-0.004 mm) 

WEIGHED PORTION OF SAMPLE 

SUSPENDED IN HEAVY LIQUID 

(AQUEOUS SOLUTION OF 

SODIUM POLYTUNGSTATE) 

S.G. = 2.85 

ISOLATE 

AND 

FILTER 

LIGHT 

FRACTION 

STORE FOR 

FUTURE 

XRD 

ANALYSIS 

Figure 1. Flow diagram outlining the procedures used to 

separate the clay, silt, and sand fractions of a sample and 

to isolate the heavy-mineral fraction for SEM/AINEDS 

analysis. 

may react with the SPT, such as calcium ions, which form 

an insoluble precipitate of calcium tungstate. After the 

decantation procedure, the silt fraction is dried in a convection oven at 60 oc. 

The separation of the heavy minerals from the silt 

fraction is performed according to the following procedure. 

1. An 82. 75-mass percent solution of SPT in water (827 .5 

g SPT in 172.5 g water equals 1,000 g solution) is 

needed to create a solution with the desired density of 

2.85 g/cm3

. Other densities (1.0-3.1) can easily be 

made by varying the mixture (fig. 2). We recommend 

adding slightly more distilled water than necessary to 

facilitate the dissolution of SPT and then evaporating 

the suspension down to the desired density in a 

convection oven set to a temperature that is less than 

60 oc. Using a higher temperature to accelerate the 

;;;-

E 

~ 

3.0 

2.85..--

2.8 

DENSITY VERSUS CONCENTRATION AT 20 oc 

~ 2.6 >-

Ic;; 

z 

~ 2.4 

70 75 80 82.7 85 

MASS PERCENT 

Figure 2. Plot of density versus the concentration of 

sodium polytungstate in distilled water at 20 oc. A solution 

with a density of 2.85 g/cm3 at 20 oc is obtained by 

preparing an 82.7 mass percent solution (e.g., 827 g solid 

and 173 g water). 

2. 

evaporation process will result in the irreversible 

decomposition of SPT into sodium tungstate, 

Na2 W04 , which is insoluble in water (unpublished 

data, J.M. Robbins, Oregon State University). 

The pH of the SPT -distilled water solution is 

about 3.2 to 4.3. If calcium carbonate is present in the 

sample to be processed, we recommend adding 

ammonium hydroxide (30 percent) until the pH is 

about 7. 0. This level limits the dissolution of the 

carbonates and the production of calcium ions that 

result in the precipitation of calcium tungstate. 

Before the silt samples are mixed with the SPT solution, 

it is necessary to prewet the samples to overcome 

surface-tension effects. Samples of known weight 

(3-4 g) are placed in preweighed, wide-mouthed·, 

glass or Teflon jars and wetted with a small amount of 

distilled water to form a slurry. Teflon containers are 

preferred because SPT sticks to glass upon drying 

and, if the suspension is accidentally brought to 

dryness, the pressure of crystallization may shatter 

glass (Savage, 1988). The jar should be evacuated to 

remove any air bubbles still adhering to the silt grains. 

The evacuation procedure is easily accomplished by 

using plastic tubing to attach a portable, rotary-vane 

vacuum pump to a rubber stopper large enough to 

replace the lid on the jar. 

3. A known weight (60 to 100 g) of SPT solution adjusted 

to a density of 2.85 g/cm3 is added to the silt/water 

slurry, and the silt sample is homogenized and disaggregated using an ultrasonic probe. A convection 

oven set to less than 60 °C can be used to evaporate 

the entire suspension to the desired density. Because 

the weight of the entire suspension and the individual 

weights of the sample, the container, and the added 

SPT solution are known, the weight of the water to be 

evaporated (that is, the water added to the sample to 

form the slurry) can be calculated. 

2 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
4. The suspension is washed into plastic centrifuge tubes 

using a squeeze bottle containing SPT solution (density, 2.85 g/cm3

). The number of centrifuge tubes 

used depends on the amount of sample to be processed. We recommend no more than 1.0 g per 

centrifuge tube because too much sample will cause 

the grains to interfere with each other and result in an 

incomplete separation. 

5. The weight of each tube is noted and adjusted using the 

stock SPT solution to ensure rotor balance in the 

centrifuge. We used an ultra-high-speed centrifuge for 

a minimum time of 10 minutes at 15,000 rpm to 

complete the separation of the heavy and light mineral 

fractions of a 4- to 62-J.Lm silt sample. 

6. After centrifugation, the separated light-mineral fraction 

floating on the surface of the heavy liquid may be 

removed from the centrifuge tubes by either of two 

techniques. First, the light-mineral fraction can be 

isolated by using a scoop, spatula, and (or) pipet and 

rinsed into a beaker using distilled water. Alternatively, the bottom 1 to 2 em of the centrifuge tube may 

be submerged in liquid nitrogen. This submersion 

freezes the heavy fraction into a plug and allows the 

unfrozen light fraction to be decanted into a beaker. 

7. The light-mineral fraction is washed out of the beaker 

with distilled water into a Millipore filtration device. 

The beaker should be thoroughly rinsed with distilled 

water to ensure that no sample remains. The material 

is suction-mounted onto preweighed 0.45-J.Lm Millipore filters and rinsed with liberal amounts of distilled 

water. Failure to wash the sample with enough distilled water will allow any remaining SPT to recrystallize in the sample and adversely affect the sample 

weight determinations. To prevent filter clogging and 

to speed the filtration process, no more than 1.0 to 1.5 

g of sediment should be mounted on any one filter. 

8. The heavy-mineral fraction contained in the centrifuge 

tubes is washed with distilled water into a beaker. 

Next, the beaker is filled with distilled water and 

ultrasonified to dissaggregate any small amount of 

calcium tungstate that may have precipitated during 

the separatory process. If present, calcium tungstate is 

usually very fine-grained and may be removed by 

decantation. The heavy minerals are rinsed with 

distilled water into the filtration device and suctionmounted onto a preweighed 0.45-J.Lm Millipore filter. 

The filter is then rinsed with liberal amounts of 

distilled water to remove any remaining SPT. 

9. The filters containing the light and heavy fractions are 

air-dried and then weighed. The weights of the lightand heavy-mineral fractions are determined by subtracting the weights of the clean filters from the 

filter-plus-sediment weights. The weight percentage 

of the heavy and light minerals in the original sample 

(step 2) is determined from the weight of the lightand heavy-mineral fraction and the weight of the 

original sediment. 

10. The filtered SPT solution diluted during the washings 

can be recovered. The solution is evaporated in a 

plastic crystallizing dish placed in an oven set to less 

than 60 oc until the density of the solution is 2.85 

g/cm3

. The recovered solution can be stored indefinitely in any tightly sealed plastic container. 

Preparation of Samples for Analysis 

Ultrasmooth carbon SEM mounts are used as the 

substrate for mounting the samples. The ultrasmooth surface prevents fine particles from being lost in voids or 

irregularities and ensures that the backscattered-electron 

signal generated from this surface is a constant, uniform 

level. A difference in backscattered-electron signal emitted 

from the sample and the carbon substrate allows the image 

analyzer to identify and measure particles. X-rays from the 

carbon matrix are not detectable by the EDS system, so 

there is no interference with characteristic X-rays from 

elements being analyzed. 

The surface of the carbon mount is covered with a 

thin coating of adhesive solution. The solution is prepared 

by dissolving the adhesive cement from a piece of cellophane tape with amy 1 acetate (Murphy, 1982). The glue 

should be allowed to become tacky before the sample is 

applied to avoid the wicking of adhesive around and over 

the particles by capillary action. 

Next, a representative split is taken from the dry, 

silt-sized, heavy-mineral separation by removing approximately one-third of the sample from a filter. The sample is 

mixed well and lightly dispersed over the surface of the 

SEM mount, being careful to minimize particle overlap and 

aggregation. This step can be performed as a dry dispersion 

by dusting the surface with the sample grains or as a wet 

dispersion by suspending the sample in distilled water and 

placing a bead of suspended sample on the mount and 

allowing it to dry. 

Once the sample mount is thoroughly dried, the 

surface is carbon-coated in a vacuum evaporator. The 

carbon coating provides an electrical path to ground when 

the electron beam of the SEM is scanned over the surface of 

the sample grains. 

Sample Analysis-Particle Size, Shape, and 

Chemistry 

The system used for the analysis of silt-sized heavy 

minerals consists of an Etec Auto scan, Model U -1 , SEM; a 

Kevex 7000 EDS system equipped with a conventional 

beryllium window detector; and a LeMont Scientific AlA 

unit (fig. 3). The sample is placed in the SEM and is 

analyzed using a beam acceleration potential of 20 ke V and 

approximately 400 picoamperes of beam current. The 

Methods 3 
X-RAY SIGNAL 

- - I 

...,X-Y DEFLECTION a BLANKING~ 

EDS 

X-RAY SPECTROMETER 

DEI ~ I ~--------~-~--. ..., 1 S~TUS 

----L_---1 SEM .,..__~llllo..-!...,.THRESHOLD -- DIGITAL 1 ~ ~ I SELECTOR :__ SCANNER .... l......___,....,....,._ ............ COMPUTER 

BACKSCATTERED 

ELECTRONS 

I I x-:v t----------t 

I ~, ,, ,~ I COORDINATE I , I 

I I 

COMPUTER 

PERIPHERALS 

: ~ ~-----~ I MONITOR l ! 

I LINE 1 

I MONITOR 1 

L.. I _____________ IMAGE ANALYZER _, I 

Figure 3. Schematic of the SEM/AINEDS system. 

specimen tilt angle is set to 0 degrees and the working 

distance is approximately 23 mm. X-ray spectra are 

acquired for 4 seconds (live time) at a takeoff angle (the 

angle between the surface of the specimen and a line 

projected to the center of the X-ray detector) of 18 degrees. 

The backscattered-electron signal is selected as the input to 

the AlA system because it gives the best ratio of signal 

(on-particle) to noise (off-particle) for samples containing 

particles that vary widely in average atomic number. 

In the SEM, the computer-driven electron beam 

automatically scans a field of particles, and the AlA system 

measures the length of a user-specified number of lines 

projected at regular angular intervals through the center of 

each particle (fig. 4). The AlA system then instructs the 

EDS unit to collect an X-ray spectrum from the center of the 

particle, identifies the peaks of elements present in the 

spectrum, and calculates the interelement peak ratios. The 

fundamental measurements for each particle (the projectedline data) are stored on computer disk along with the 

element data. From the fundamental particle data, the AlA 

system automatically calculates user-selected parameters, 

or derived physical measurements, such as area, average 

diameter, length, width, and (or) length-to-width ratio, for 

each of the particles. The derived physical measurements 

calculated for each particle can be sorted by chemistry into 

categories by the system's chemistry definition file and 

output as histograms and statistical tables. 

A chemistry definition file consists of user-defined 

chemical categories called macro classes that allow measured particles to be sorted according to composition by their 

relative elemental X-ray intensities. Each macro class 

represents a specific mineral or a series of minerals of 

similar composition. Table 1 is a partial listing of actual 

computer output showing macro classes created to sort 

X-ray spectral data collected from particulate samples from 

the test study area (see below). For example, macro class 1 

defines the relative X-ray intensity criteria for titanium 

oxide minerals (rutile, leucoxene, anatase, brookite, etc.). 

For a particle to fit this macro class, the X-ray spectrum 

must meet three criteria. First, the X-ray spectrum of the 

particle must contain a titanium peak. Second, the ratio of 

the titanium X-ray peak intensity to the sum of all the 

element intensities (including titanium) measured in the 

spectrum must be equal to or greater than 0. 6 and equal to 

or less than 1.0. This criterion sets both the lower and upper 

limits because the titanium peak must contain at least 60 

percent of all X-ray peak counts and can contain up to 100 

percent of all counts. Third, the ratio of X-ray peak 

intensities from any one of the other elements to all the 

elements (including titanium) in the spectrum must be equal 

to or less than 0.05. Thus, the upper limit for the individual 

peak intensities for each of the other elements cannot 

exceed 5 percent of the total counts. 

As each macro class is created, the user may enter a 

specific gravity for that class. Because each particle is 

sorted according to its chemistry and is stored in a class 

along with its derived physical measurements, weight 

percentages of minerals (macro classes) can be calculated. 

For example, the weight percentage of particles within a 

specific size range of a chemical category can be calculated 

by summing the masses of all the measured particles sorted 

into that size range, dividing that sum by the total sample 

mass (the total mass of all particles measured), and multiplying by 100. The mass of each particle is equal to its 

volume times the value of the specific gravity entered by the 

user for that chemical category. The algorithm used for the 

4 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
BACKSCATTER 

ELECTRON IMAGE 

SEM 

ELECTRON GUN 

DEFL ~ 

....---FULL SCAN---. 

ENERGY DISPERSIVE 

SPECTROMETER SYSTEM 

R= 4SEC 11659 l N' 

•1824 H•28KEU I , 18 A8•28KEU 18 

EOS SPECTRUN • !NENITE 

Til FE 

171"" _j 

[ ~ -.. -. :p~~ .. ~ ~6R. 'E~~~-- ~~R~i~~~:· ~~~~~~~~ · } 

I. . M:~:~,REMENrs ··• ~~~~~sfJ~f~J~R~t~~tr~?r~ > •::_!_ 

b. Avg. diameter .. . . .. · ... .. · · · .. · · ... ·.. 

1 c. Width ....... 

d. Length ···· 

e. Width I I ength , ...... ELEMENT IDENTIFICATION 

AND CALCULATION OF 

PEAK RATIOS 

I ..,..,.,_~~~,.,.,.,..,.=""'.,..,.,.,.. ' .. .. ....... .. . .......... ~~~~~ ........ :::::::::::::::: 

I 

,. SORTING OF 

MEASURED 

PARTICLES ···· · BY CHEMISTRY 

CHEMISTRY 

DEFINITION 

FILES 

Figure 4. Flow diagram of procedures performed during SEM/AINEDS analysis . 

calculation of 4/3-rr* · SA · 5B* · 5B the particle volume is based on the assumption that the two-dimensional particle is an ellipse with its 

length the major axis, A, and its width the minor axis, B. 

Rotation of the ellipse about its major axis creates a prolate 

spheroid with a volume equal to 

Based on the shapes of mineral grains from the samples 

observed in the SEM, this mathematical model is an 

acceptable routine to estimate particle volume. 

Methods 5 
Table 1. Partial list of user-defined chemical categories 

[The chemical categories are programmed into the chemical definition file and represent a specific mineral or a series of minerals] 

Specification type 

Ti oxides, MACRO CLASS 1 

Ti fraction of X-ray count 

Other element fractions: 

i.e., NAMGALSI P SCL KCACRMNFENICUZNPB 

lower limit 

0.600 

0.000 

Upper limit 

1.000 

0.050 

(Weighting) 

1000 

1000 

Parameter statistics provided along with histograms and tables 

Specific gravity =4.200 

Fe Ti oxide, MACRO CLASS 2 

Fe fraction of X-ray count 

Ti fraction of X-ray count 

Other element fractions: 

i.e., NAMGALSI P SCL KCACRMNNICUZNPB 

0.100 

0.100 

0.000 

1.000 

1.000 

0.050 

1000 

1000 

1000 

Parameter statistics provided along with histograms and tables 

Specific gravity =4.700 

Ca Ti Silicate, MACRO CLASS 3 

Ca fraction of X-ray count 

Ti fraction of X-ray count 

Si fraction of X-ray count 

Other element fractions: 

i.e., NAMGAL P SCL KCRMNFENICUZNPB 

0.100 

0.100 

0.050 

0.000 

1.000 

1.000 

1.000 

0.020 

1000 

1000 

1000 

1000 

Parameter statistics provided along with histograms and tables 

Specific gravity =3.500 

Table 2 lists the chemical categories (macro classes) 

as they appear in the chemistry definition file prepared for 

the test study area on the Outer Continental Shelf near 

Georges Banlc Minerals corresponding to each macro class 

are also tabulated. The parameters for each macro class are 

based on chemical criteria that may fit a number of minerals 

that have overlapping compositions. If necessary, further 

refinement of the mineralogy within each macro class is 

accomplished by X-ray diffraction analysis (XRD) and 

examination of particle morphology in the SEM. Two 

macro classes, Si Oxide and Fe Stain Si Ox., represent 

quartz and iron-stained quartz, respectively. A small but 

significant number of quartz grains adhered to the wall of 

the test tube or to the heavy-mineral grains during the 

heavy-liquid separation procedure and were not separated 

with the other light-mineral grains. 

A 10-A phyllosilicate group is included in the chemistry definition file for the purpose of particle identification, 

but the mathematical model listed above is not appropriate 

for the calculation of weight percentages of micaceous 

minerals. Furthermore, the separation of phyllosilicates 

using heavy liquids is problematic because the specific 

gravities of the micas often straddle that of the heavy liquid 

and not all of the grains are removed in the heavy-mineral 

residue. As a result, the K AI Silicate macro class data 

have been removed from the weight percentages shown in 

table 5. 

To evaluate the ability of the image analysis system to 

sort particles by chemistry into predefined chemical categories, we prepared a sample mount containing a known 

number of particles from five different minerals. The results 

in table 3 show that the image analysis system properly 

classified 90 of the 93 mineral grains (over 96 percent of the 

grains) mounted for the test. The system was not able to 

classify three of the grains because of their rough surface 

Table 2. List of chemical categories or macro classes 

[These macro classes were prepared for the test study area off southeastern 

New England. Minerals corresponding to each macro class are also 

tabulated] 

Macro Class 

1. Ti Oxide 

2. Fe Ti Oxide 

3. Ca ti Silicate 

4. Mg Carb. 

5. AI Oxide 

6. Fe Oxide/Carb. 

7. Si Oxide 

8. Zr Si Oxide 

9. Ca Phosphate 

10. Fe Zn Cu Sulph. 

11. Ca AI Silicate 

12. CaFe Silicate 

13. Fe AI Silicate 

14. AI Silicates 

15. Fe Stain Si Ox. 

16. Na Ca Mg Sil. 

17. K AI Silicate 

18. Mg AI Oxide 

19. Fe Mn Oxide 

20. Mise. Macro 

Mineral(s) 

Rutile, leucoxene, anatase, brookite 

Ilmenite 

Sphene 

Magnesite 

Corundum 

Magnetite, hematite, goethite, siderite 

Quartz 

Zircon 

Apatite, monazite, vivianite 

Pyrite, sphalerite, chalcopyrite 

Epidote 

Andradite (garnet) 

Staurolite, almandine (garnet) 

Sillimanite, topaz, beryl, andalusite, 

spodumene, kyanite 

Iron-stained quartz 

Amphibole, pyroxene, tourmaline 

10-A phyllosilicate group 

Spinel 

Ferromanganese 

Other minerals 

6 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
RHODE 

CONNECTICUT 

~~ NANTUCKET 

71°W 

WEIGHT PERCENTAGE HEAVY 

MINERALS IN THE SILT 

<5% ~ 

5-6% ~ 

>6-9% ~ 

>9% 

GEORGES 

BANK 

Figure 5. Sample locations of surficial sediments collected in the test study area. Patterned areas show the weight 

percentage of heavy minerals in the silt fraction. Samples from locations marked by large dots with identification 

numbers were analyzed by SEM/AINEDS analysis. 

topography and the low, 18-degree, X-ray takeoff angle 

used in our SEM/EDS unit. After the system locates and 

measures a grain, it centers the beam on the grain to collect 

a spectrum. Occasionally, this location is in a recess on the 

surface, and the X-ray path to the EDS detector is 

obstructed. However, this obstruction is less of a problem 

with most newer SEM/EDS systems because they are 

equipped with inclined EDS detectors that allow the X-rays 

to be collected at takeoff angles of 35 to 40 degrees. 

TEST STUDY AREA- RESULTS AND 

DISCUSSION 

Mineralogical studies were made on the silt fraction 

of the surficial sediment from the Outer Continental Shelf 

area near Georges Bank (fig. 5). The area map shows 

sample locations (large and small dots) of surficial sediments collected in the study area and the weight percentage 

of heavy minerals in the silt fraction. The percentages were 

calculated from samples collected from all locations. Table 

4 lists the weight percentages of silt-sized heavy minerals 

and compares them with data on the sand fraction listed in 

Hathaway (1971) and Poppe and others (1991). Samples 

from the map locations marked with identification numbers 

were analyzed by SEMI AIA/EDS analysis, and selected 

examples of actual data output for sample station N5 are 

shown in figures 6-10. Figures 6-8 illustrate how the 

particle count data can be sorted either in terms of numbers 

of particles or in percentages of the total population into size 

ranges for each chemical category. Weight percentage data 

are presented in figures 9 and 10. The relative abundances 

of the nonmicaceous, heavy minerals contained in the silt 

fraction for all of the sample locations numbered on the 

map are presented in table 5. The mineralogy and the 

Table 3. Results from a test sample, particles mounted 

versus identified 

[Test results from a specially prepared SEM mount showing the number of 

particles identified and sorted by the automatic image analyzer system into 

macro classes or mineral groups versus the actual number mounted for 

each mineral] 

Mineral Macro Number Number 

class mounted counted 

Rutile Ti Oxide 14 14 

Apatite Ca Phosphate 19 19 

Pyrite Fe Zn Cu Sulph. 19 19 

Epidote Ca Al Silicate 20 19 

Topaz Al Silicates 21 19 

Total mineral grains 93 90 

Test Study Area-Results and Discussion 7 
Table 4. Weight percentages of silt-sized minerals from test area 

[Weight percentages of silt-sized light and heavy minerals determined by the heavy-liquid separation technique for samples collected from the Continental 

Shelf off southeastern New England. Sand-sized, heavy-mineral data are presented for comparison. Dashes (-)in data columns denote no data] 

Silt fraction weight % Sand fraction weight % Whole sample weight (%) 

Sample 

number1 Whole Light Heavy Heavy Silt-sized Silt + sand-sized 

sample minerals minerals minerals heavy minerals heavy minerals 

N5 12.7 89.18 10.82 21.6 1.37 2.6 

N6 10.0 90.59 9.41 .94 

N11-1 23.6 88.55 11.45 2.70 

Nll-2 23.6 88.75 11.25 2.66 

Nll-3 23.6 88.96 11.04 2.61 

N12-1 9.2 88.25 11.75 32.4 1.08 3.1 

N12-2 9.2 88.85 11.15 1.03 

N12-3 9.2 88.62 11.38 1.05 

N17 10.3 91.40 8.40 .87 

N18 25.3 91.00 9.00 2.28 

N19 31.4 90.89 9.11 2.86 

N20-1 44.8 91.06 8.94 31.8 4.01 4.8 

N20-2 44.8 90.75 9.25 4.14 

N20-3 44.8 91.03 8.97 4.02 

N24-1 38.9 92.73 7.27 31.8 2.83 3.6 

N24-2 38.9 92.42 7.58 2.95 

N24-3 38.9 92.91 7.09 2.76 

N31 14.1 92.94 7.06 1.00 

N32 24.1 91.89 8.11 1.95 

N33 25.3 94.10 5.90 1.49 

N34 49.0 93.97 6.03 2.95 

N35-1 72.3 94.56 5.44 3

2.1 3.93 4.2 

N35-2 72.3 94.57 5.43 3.93 

N35-3 72.3 94.91 5.09 3.68 

N36 10.2 93.17 6.83 21.4 .70 1.9 

N38 31.8 93.77 6.23 1.98 

N39 66.4 96.62 3.38 2.4 2.24 2.3 

N40 61.6 96.25 3.75 2.31 

N41 62.6 95.67 4.33 2.5 2.71 2.8 

N42-1 29.7 94.53 5.47 1.62 

N42-2 29.7 94.21 5.79 1.72 

N48 8.5 94.55 5.45 2.2 .46 .6 

N49 61.0 94.90 5.10 3.11 

N50 69.3 95.53 4.47 3.10 

N51-1 49.0 95.74 4.26 2.09 

N51-2 49.0 95.55 4.45 2.18 

N52 17.5 93.95 6.05 21.5 1.06 2.1 

N56 8.4 94.39 5.61 .47 

N57 23.6 94.94 5.06 1.19 2.9 

N58 35.3 95.78 4.22 1.49 

N59 19.5 95.79 4.21 2.3 .82 1.0 

N60-1 16.1 94.76 5.24 .84 

N60-2 16.1 94.11 5.89 .94 

N60-3 16.1 94.16 5.84 .94 

N64 6.1 94.19 5.81 .35 

1066-1 15.9 94.29 5.71 .91 

1066-2 15.9 94.11 5.89 .94 

1067 51.4 94.92 5.08 2

2.6 2.61 3.5 

1069 17.4 94.55 5.45 .94 

1083-1 18.6 94.75 5.25 .98 

1083-2 18.6 94.96 5.04 .94 

1083-3 18.6 94.87 5.13 .95 

1

For the purpose of computerized sorting and searches, the data base reported in Hathaway (1971) uses station numbers of standardized length for 

the samples used in this study, e.g., N005 for N5 and NOll for Nll. The shorter style is used here for conformity with the usage in Poppe and others 

(1991). Hyphenated sample numbers denote replicate analyses. 2 Data from Hathaway (1971). 3 Data from Poppe and others (1991). 

8 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
-1 

tD 

~ 

~ c 

c.. 

-< 

> 

~ I» 

I 

~ 

tD 

Ill 

c 

if 

I» 

::s 

c.. 

c 

iii" 

I") 

c 

Ill 

Ill 

s· 

::s 

\C 

Table 5. Abundances of nonmicaceous, silt-sized heavy minerals in samples from the test study area 

[The samples analyzed were surficial sediment samples collected from the Continental Shelf off southeastern New England (fig. 5). The mineralogy is based on data from the chemical class information 

from SEM/AIA/EDS analysis, observation of particle grain morphology in the SEM, and XRD. The values are in weight percent and are normalized to sum to 100. Asterisks indicate heavy minerals 

determined by XRD] 

Sample ID N5 N11 N12 N18 N20 N24 N33 N36 N39 N41 N48 N51 N57 N59 1067 1083 

Rutile-anatase-brookite 5.74 6.17 5.42 5.69 5.29 10.50 6.70 8.57 7.41 3.81 3.98 6.07 3.73 5.00 1.97 4.73 

Ilmenite 43.42 33.56 33.98 42.39 26.69 29.69 28.05 28.39 31.90 20.78 23.04 20.59 20.14 21.39 20.14 19.80 

Sphene 0.53 0.38 2.38 0.69 2.73 0.95 0.05 0.11 6.87 0.60 4.45 2.10 3.19 1.67 1.48 2.84 

Corundum 0.00 0.17 0.23 0.00 0.30 0.02 0.00 2.15 0.00 0.00 0.00 0.56 0.00 0.00 0.25 0.00 

Magnetite-hematite-goethite-siderite 0.78 7.20 7.78 2.57 2.09 7.10 6.15 3.94 2.82 2.33 8.21 8.01 6.30 1.15 1.53 8.08 

Zircon 20.30 8.37 13.83 5.07 6.59 3.54 9.41 3.90 0.51 2.11 8.70 5.85 3.06 2.32 4.98 0.25 

Apatite-monazite-vivianite 0.00 0.62 0.46 0.71 1.19 2.67 0.76 6.26 0.28 1.01 2.58 0.79 2.62 2.50 2.48 2.25 

Pyrite 0.32 0.08 0.40 1.62 0.00 0.21 1.81 0.06 0.78 0.04 0.05 0.11 2.34 1.67 1.28 3.74 

Spinel 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

Epidote 5.45 5.63 4.44 9.26 6.22 6.07 11.11 9.07 6.87 12.08 7.93 11.79 10.93 7.67 14.98 8.58 

Garnet -staurolite 2.91 7.44 7.32 2.96 12.15 6.46 13.34 2.55 5.08 6.69 5.28 7.73 8.92 10.84 9.02 10.16 

Sillimanite-beryl-andalusite-topaz- 2.57 2.29 1.01 2.96 1.91 3.56 2.18 0.91 1.10 4.12 3.42 2.88 1.70 6.51 4.54 2.39 

spodumene-kyanite 

Amphiboles 5.36 10.80 6.96 7.27 18.88 9.92 6.70 14.79 12.93 15.51 9.64 16.28 13.61 20.23 12.55 17.47 

Pyroxenes 0.77 6.10 5.56 3.64 3.44 3.30 1.67 1.68 4.84 8.61 4.17 5.66 4.78 6.13 3.72 4.11 

Tourmaline 3.57 1.88 2.78 4.85 3.42 1.98 3.90 3.36 4.04 10.33 1.93 3.54 4.77 4.29 2.79 7.71 

Other FeMn coated-rock fragments 8.28 9.31 7.45 12.09 9.10 14.03 8.17 14.26 14.57 11.97 6.62 8.04 13.91 8.63 18.24 7.90 
SAMPLE ID: SILT-SIZE HEAVY MINERALS N5 13-·SEP-91 

POPULATION PERCENT VS. CHEMICAL CLASS 

1 

TYP CLASS NAME % 0 1 2 3 4 5 6 7 8 9 0 

-------------------------o----o----o----o----o----o----o----o----o----o----0 

MACR TI OXIDES 4.55[** 

MACR FE TI OXIDE 29.55[*************** 

MACR CA TI SILICATE 0.65[ 

MACR MG CARBONATE 0.00[ 

MACR AL OXIDE 0.00[ 

MACR FE OXIDE/CARB. 1.95[* 

MACR SI OXIDE 3.25[** 

MACR ZR SI OXIDE 12.01[****** 

MACR CA PHOSPHATES 0.00[ 

MACR FE ZN CU SULPH 1.30[* 

•suB cu-s o.ooc •SUB ZN-S 0.00[ 

*SUB FE-S 0.97[ 

MACR CA AL SILICATE 5.84[*** 

MACR CA FE SILICATE 1.95[* 

MACR FE AL SILICATE 1.95[* 

MACR AL SILICATES 2.~7[* 

MACR FE STAIN SI OX 0.97[ 

MACR NA CA MG SIL. 13.96[******* 

MACR K AL SILICATE 0.00[ 

MACR MG Al OXIDE 0.00[ 

MACR FE MN OXIDE 0.97[ 

MACR MISC. MACRO 18.83[********* 

MACR SUM UNKNOWN 0.00[ 

Figure 6. Histogram of particle population percent versus chemical class (macro class). [Actual 

data output from the image analysis program for a sample collected from station N5 in the test 

study area (fig. 5).] 

SAI'IPLE ID: SILT--SIZE HEAVY MINERALS N5 13--SEP-'H 

1'-IUI'IBER OF PAr\TICLES f.IY CHEM.ISTRY AND AVERAGE DIAI'IETER <UI'I.) F~AtmE 

CHEI'IICAL CATEGORY \ 4.00 ( 8.00 <H ... 00 (31. 00 (E,(.~. 00 >62.00 I TOTAL 

E 0 E 0 E 0 E 0 E 0 E 0 

------------------------------------------- TI OXIDES 0 0 0 0 8 f:.. 14 

FE TI OXIDE 0 1 3 2 38 '•7 91 

CA TI SILICATE 0 0 0 0 2 0 2 

MG CARBONATE 0 0 0 0 0 0 0 

AL OXIDE 0 0 0 0 0 0 0 

FE OXIDE/CARB. 0 1 0 1 3 1 b 

~3! OXIDE 0 4 0 1 2 3 10 

zr< SI OXIDE 0 0 0 0 1"" ~~ 2f~ 37 

CA PHOSPHATES 0 0 0 0 0 0 0 

FE ZN cu SULPH 0 2 1 0 0 1 4 

CA AL SILICATE 1 1 0 0 10 E. 18 

CA FE SILICATE 0 0 1 0 3 C! b 

FE AL SILICATE 0 1 1 0 4 0 E. 

AL SILICATES 0 2 0 1 0 It 7 

FE STAIN SI ox 0 0 0 0 0 3 3 

NA CA I'IG SIL. 0 2 3 3 20 15 43 

I~ AL SILICATE 0 0 0 0 0 0 0 

I'IG AL OXIDE 0 0 0 0 0 0 0 

FE I'IN OXIDE 0 0 0 0 2 1 3 

I'IISC. MACRO .,. 

~~ f, 3 It t=~3 17 58 

SUM UNKNOWN 0 

TOTAL E. 20 12 12 130 128 308 

Figure 7. The number of particles in user-specified size ranges within each chemical category. 

Symbols "E 0" in the column headings are exponential notation for ten raised to the zero 

power, or 10°=1. The numerical values in the headings are equal to the number indicated times 

ten raised to the power shown. [Actual data output from the image analysis program for a sample 

collected from station N5 in the test study area (fig. 5). UM. =Micrometers.] 

10 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
SAMPLE ID: SILT-SIZE HEAVY MINERALS N5 lJ····SEP-··'31 

PERCENT OF TOTAL PARTICLES BY CHEMISTRY AND AVERAGE DIAMETER CUM.) RANGE 

C II E 1•11 C n L C n T F G 0 F~ Y \ < 4 • 0 0 < g • 0 0 < 1 E, • 0 0 < 3 :1 .• 0 0 < L ;:.~ .. 0 0 > E, i:.' • 0 (";~ I T 0 T (l L.. 

E 0 E 0 E 0 E 0 E 0 E 0 

----------------------------- ....................... 

TI OX I DE::> 0. 0 .. 0. 0. ~~ .. t;,O :l. ')'.5 .It. c:·1::-

... J ~J 

FE TI OXIDE 0. o. 3E~ 0. ':!'? 0. t.:. ~-:J :1.(:·:. ;;).t+ 1 ~.·; .. c.~(::, [:~9 • t:·t:· 

..J .J 

en ri ~:; IL [CnTE o. 0. 0. (). 0. E, ~.5 o. o. E,~:i 

I•IC:; cnr~DOt-!(lTE o. 0. 0. 0 .. 0. 0 .. 0. 

AL OXIDE o. o. o. 0. 0. 0. o. 

FE OX I DE::/Cm~I<. 0. 0. 32 0. o. 3i.:? 0. '0/ o. 3i.":~ :!.. r)~i 

:; I OXIDE 0. :1.. :30 o. 0. 3;:~ 0. (;'.s () .. ')) 3. 'JL":' (.; .... J 

zr-~ bJ OXIDE 0. 0. 0. 0. .ft .. g} 7 .. :I. A 1 c!. • Ol 

en PI !O::>PHATE~; 0. 0. o. 0. 0. 0 .. 0 .. r:·r: ZH cu !3l.J!...PH o. o. C'5 0. 3;:~ 0. 0. o. 3;:~ 1. ]() 

en (ll.. ~>ILICtHE o. 32 o. 32 0. 0 .. :s. .···,r.:· i:: .... J l. 9~:_; ~:j .. El'• en FE ~:;ILICATE 0. 0 .. o. 32 o. 0. ')'? o. 6~5 l.. 'J~:i 

FE nL ~;I L. I C(lTE o. 0. 3f.~ 0. 3P o. :1. .. 30 ·~-· :1 ... ·~)::.; 

m .. SILJCATES 0. 0. (;,~5 0. 0. 3(~ o. 1. 30 .--, 

t:: ... 27 

FE ~>TniH SI ox o. o. 0. o. () .. 0. ')/ 0. 97 

HA CA t•IG :;IL. 0. o. (;,~5 o. 'J'7 0. 'J'l tJ. '•') '•. H'l :1. 3. ')(; 

K m_ SILICATE 0. o. 0. o. 0. 0 .. 0. 

lvJG nL OXIDE 0. 0. 0. o. 0. (). 0. 

r:·E J•Jt-1 OXIDE o. o. o. 0. 0 .. f.,~·; 0. 3f.:.~ 0. '.n 

11 I !)C. 11nct:;:n 1. 6f.~ 1. ':J!':i o. ')'7 1. 30 7. 4'7 !!:' ,J. 5(~ 18. B3 

bLJI•I Ut-IKHOWI·~ o. 00 

TDHH. 1 . 9~i E.. •t ';;J ~-s. r;;)(> 3. 90 "~;-.:: .. F~ :1. .It :I.. ~:;t:: .. l 00. 00 

Figure 8. The percentage of total particles in size ranges for each chemical category. Symbols 11 E 0" in the column headings are exponential notation for ten raised to the zero power, or 

10°=1. The numerical values in the headings are equal to the number indicated times ten raised 

to the power shown. [Actual data output from the image analysis program for a sample collected 

from station N5 in the test study area (fig. 5). UM.=Micrometers.] 

SAMPLE ID: SILT-SIZE HEAVY MINERALS N5 13--SEP-91 

WEIGHT PERCENT VS. CHEMICAL CLASS 

1 

TYP CLASS HAME % 0 1 2 3 4 5 6 7 8 9 0 

-------------------------0----o----o----o----o----o----o----o----o----o----o 

MACR TI OXIDES 5.13[*** 

MACR FE TI OXIDE 39.85[******************** 

MACR CA TI SILICATE 0.48[ 

MACR MG CARI<ONATE O.OOC 

MACR AL OXIDE 0.00[ 

MACR FE OXIDE/CARB. 1.82[* 

MACR SI OXIDE 1.38[* 

M(lCR ZR SI OXIDE 17.99[********* 

MACR CA PHOSPHATES 0.00[ 

MACR FE ZN CU SULPH 0.34[ 

*SUB cu-s o.ooc 

*SUB ZN-S 0.00[ 

*SUB FE-S 0.03[ 

MACR CA AL SILICATE 4.88[** 

MACR CA FE SILICATE 1.68[* 

MACR FE AL SILICATE 1.1€.[* 

MACR AL SILICATES 2.27[* 

MACR FE STAIN SI OX 1.07[* 

MACR NA CA MG SIL. 9.9E.C***** 

MACR K AL SILICATE 0.00[ 

MACR MG AL OXIDE 0.00[ 

MACR FE MN OXIDE 1.29[* 

MACR MISC. MACRO 10.'71[***** 

MACR SUM UNKNOWN 0.00[ 

Figure 9. A histogram of weight percentages versus chemical category. [Actual data output 

from the image analysis program for a sample collected from station N5 in the test study area 

(fig. 5).] 

Test Study Area-Results and Discussion 11 
BAI'IPLE ID: SILT-·SIZE l·iEAVY IHNEF<ALS N5 13·-SEP-91 

WEIGIH PERCENT OF TOTAL SAMPLE BY CHEMISTRY AND AVERAGE DH~I'IETER <UI'I.) RANGE 

CHEMICAL CATEGORY ' < 4.00 < 8.00 <H .. 00 {31. 00 {f,2.00 >f,2. 00 I TOTAL 

E 0 E 0 E 0 E 0 E 0 E 0 

------------------------------------------- TI OXIDES 0. o. o. o. 2.10 3.03 5.13 

FE TI OXIDE o. 0.01 0.04 0.18 11. [~9 28. :-s4 39.85 

CA TI SILICATE o. o. o. 0. 0.48 o. 0.48 

I'IG CARBONATE o. o. o. 0. 0. o. o. 

AL OXIDE o. o. o. 0. 0. o. o. 

FE OXIDE/CARB. o. o.oo 0. 0.03 1. 1E. 0.(:,3 1.82 

SI OXIDE o. 0.01 0. 0.02 0.40 o. 9~i 1.38 

ZR SI OXIDE 0. o. o. o. 5.1€. 12.82 17.99 

CA PHOSPHATES 0. 0. o. o. o. 0. o. 

FE ZN cu SULPH 0. 0.01 0.01 o. o. 0.32 0.34 

CA AL SILICATE 0.00 0.00 o. o. [~. 10 2.77 4.88 

CA FE SILICATE 0. 0. 0.02 o. 0.71 0.95 1.€.8 

FE AL SILICATE o. 0.01 0.01 o. 1. 1~i o. 1.16 

AL SILICATES o. 0.01 o. 0.03 o. 2.24 2.27 

FE STAIN SI ox o. o. o. o. o. 1.07 1. 07 

NA CA I'IG SIL. o. 0.00 0.03 0.12 3.29 E.. 52 9.96 

K AL SILICATE o. o. o. o. o. o. o. 

MG AL OXIDE o. o. o. o. o. o. o. 

FE I'IN OXIDE o. o. o. 0. 0.(:,4 O.E.5 1.29 

MISC. I'IACRO 0.00 0.01 0.03 0.12 4.58 ~i. 97 10.71 

SUM UNKNOWN 0.00 

TOTAL 0.00 0.0(:, 0.14 0.50 33.05 E.E..25 100.00 

Figure 10. Weight percentages for size ranges within each chemical category. Symbols "E 0" in 

the column headings are exponential notation for ten raised to the zero power, or 10°=1. The 

numerical values in the headings are equal to the number indicated times ten raised to the 

power shown. [Actual data output from the image analysis program for a sample collected from 

station NS in the test study area (fig. 5). UM.=Micrometers.] 

abundances are derived from the chemical category (macro 

class) information from SEM/AIA/EDS analysis, from the 

observation of particle grain morphology in the SEM, and 

from XRD. 

Poppe and others ( 1991) discuss the scientific relevance of the data listed in this report. The scientific study 

has revealed several important relationships with regard to 

the composition, abundance, and areal distribution of siltand sand-sized heavy minerals in a modern depositional 

environment on the New England Continental Shelf. Some 

of the relationships are listed below. 

1. Regardless of sediment texture, heavy minerals constitute a substantially greater weight percentage of the 

silt fraction than that of the sand fraction (table 4). 

2. The silt-sized heavy mineral assemblage is diverse, is 

predominately detrital, and reflects the metamorphic 

and igneous character of the bedrock of New England 

and eastern Canada (table 5). The presence of extensively weathered ilmenite grains suggests that the 

provenance may also contain a sedimentary component. 

3. There are pronounced compositional differences 

tween the mineralogies of the silt and sand fractions. 

For example, corundum and the Ti02 , epidote, and 

phosphate groups are enriched in the silt fraction (table 5); spinel and the amphibole, garnet + 

staurolite, and aluminum silicate groups are relatively 

concentrated in the sand fraction (Ross, 1970; Hathaway, 1971). 

4. Ti02 is enriched in the silty sands southwest of 

Nantucket Shoals (fig. 5 and table 5). These sediments should be evaluated further for their economic 

potential. 

SUMMARY 

We have employed a new, nontoxic, heavy-liquid 

medium, an aqueous solution of SPT, to simplify the 

procedures necessary to separate silt-sized minerals by 

specific gravity. Samples of the silt-sized, heavy-mineral 

fraction were prepared for examination in a SEM equipped 

with an AlA and EDS system. Hundreds of particles within 

each sample were sized and sorted according to chemistry, 

and statistical data were output in histograms and tables. 

Chemical categories can be carefully designed by the user to 

simulate distinct minerals or mineral groups. Because of our 

scientific interests, the study area chosen was in a marine 

environment, but the same techniques can be employed on 

sediments from other environments. Particle feature analysis makes it possible to sort large numbers of particles by 

size and chemistry. Most manufacturers of current energydispersive X-ray equipment offer optional particle feature 

hardware and software as part of the digital imaging 

package. 

12 Separation and Identification of the Silt-Sized Heavy-Mineral Fraction in Sediments 
REFERENCES CITED 

Callahan, J., 1987, A nontoxic heavy liquid and inexpensive 

filters for separation of mineral grains: Journal of Sedimentary Petrology, v. 57, no. 4, pp. 765-766. 

Emery, K.O., 1966, Atlantic continental shelf and slope of the 

United States-Geologic background: U.S. Geological Survey Professional Paper 529-A, 23 p. 

Folk, R.L., 1974, Petrology of sedimentary rocks: Austin, Hemphill, 192 p. 

Gregory, M.R., and Johnston, K.A., 1987, A nontoxic substitute 

for hazardous heavy liquids-Aqueous sodium polytungstate 

solution: New Zealand Journal of Geology and Geophysics, 

v. 30, pp. 317-330. 

Hathaway, J. C. , 1971 , Data File-Continental Margin Program, 

Atlantic coast of the United States: Woods Hole Oceanographic Technical Report 71-15, 496 p. 

Murphy, J.A., 1982, Considerations, materials, and procedures 

for specimen mounting prior to scanning electron microscopic examination: Scanning Electron Microscopy, pp. 

657-696. 

Poppe, L.J., Commeau, J.A., and Valentine, P.C., 1991, Mineralogy of the silt fraction in surficial sediments from the 

Outer Continental Shelf off southeastern New England: 

Journal Sedimentary Petrology, v. 61, no. 1, pp. 54-64. 

Ross, D.A., 1970, Atlantic Continental Shelf and slope of the 

United States-Heavy minerals of the continental margin 

from Nova Scotia to northern New Jersey: U.S. Geological 

Survey Professional Paper 529-G, 40 p. 

Savage, N.M., 1988, The use of sodium polytungstate for 

conodont separations: Journal of Micropaleontology, v. 7, 

no. 1, pp. 39-40. 

References Cited 13 



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Maps 

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 7.5- or 15-minute quadrangle formats (scales 

mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include 

structure and columnar sections only. 

Geophysical Investigations Maps are on topographic or planimetric bases at various scales; they show results of surveys using 

geophysical techniques, such as gravity, magnetic, seismic, or radioactivity, which reflect subsurface structures that are of economic or 

geologic significance. Many maps include correlations with the geology. 

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also 

includes 7 .5-minute quadrangle photogeologic maps on planimetric 

bases that show geology as interpreted from aerial photographs. Series 

also includes maps of Mars and the Moon. 

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial 

geology, stratigraphy, and structural relations in certain coal-resource 

areas. 

Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum 

potential. 

Miscellaneous Field Studies Maps are multicolor or blackand-white maps on topographic or planimetric bases on quadrangle or 

irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations. 

Hydrologic Investigations Atlases are multicolored or blackand-white maps on topographic or planimetric bases presenting a wide 

range of geohydrologic data of both regular and irregular areas; 

principal scale is 1:24,000, and regional studies are at 1:250,000 scale 

or smaller. 

Catalogs 

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, 

Books and Open-File Reports Section, Federal Center, Box 25425, 

Denver, CO 80225. (See latest Price and Availability List.) 

"Publications of the Geological Survey, 1879-1961" may be 

purchased by mail and over the counter in paperback book form and as 

a set of microfiche. 

"Publications of the Geological Survey, 1962-1970" may be 

purchased by mail and over the counter in paperback book form and as 

a set of microfiche. 

"Publications of the U.S. Geological Survey, 1971-1981" may 

be purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by 

mail and over the counter in paperback book form. 

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by 

mail and over the counter in paperback booklet form only. 

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback 

booklet form only. 

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" are available free of charge by mail or may 

be obtained over the counter in paperback booklet form only. Those 

wishing a free subscription to the monthly catalog "New Publications of 

the U.S. Geological Survey" should write to the U.S. Geological 

Survey, 582 National Center, Reston, VA 22092. 

Note.-Prices of Government publications listed in older catalogs, announcements, and publications may be incorrect. Therefore, 

the prices charged may differ from the prices in catalogs, announcements, and publications.