Shale disaggregation

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To all interested in disaggregating shales using Quaternary-O substitutes:

Below is a copy of a short methods paper I published in Journal of
Paleontology a couple of years ago [67(1),1993, pp. 154-155].  I hope it
helps out!


TECHNIQUE FOR DISAGGREGATING MUDSTONES TO RETRIEVE MICROFOSSILS AND
NON-CLAY RESIDUAL PARTICLES

        This technique is effective for completely breaking down moderately
calcareous to non-calcareous mudstones and shales to produce a concentrated
residue of microfossils and non-clay minerals.  I have applied this
treatment to Mississippian and Pennsylvanian age mudstones and have easily
retrieved abundant conodonts, ostracods, forams, spores, wood fragments,
fish teeth, vertebrate bone fragments, silt, mica, pyrite crystals and
framboids, and phosphate nodules.  All of the above items emerge from the
treatment with fine structures such as spines and surface ornamentation
undamaged and completely free of surficial clay.  This technique is a
modification of that of Lund (1970).  The chemical used by Lund (Union
Carbide Amine 220) is no longer manufactured and an effective alternative
is reported here.  Furthermore, the additional steps in processing reported
here increase the efficacity of the technique for completely dissolving
indurated mudstones.
        Two chemicals are needed for this procedure.  The first is an
industrial surfactant called Amine-O
[2-(8-heptadecenyl)-4,5-dihydro-1h-imidazole-1-ethanol].  It is available
in 5 lb quantities from Ciba-Geigy Chemical.  The second is
Methyl-Amyl-Alcohol (also called Methyl Isobutyl Carbinol or
4-Methyl-2-pentanol) which can be purchased from Pfaltz and Bauer.  While
neither of these chemicals is extremely dangerous, both are moderately
caustic and gloves and eye protection should be worn when working with
them.  Furthermore, Methyl-Amyl-OH gives off noxious fumes as it
evaporates.  This procedure should be performed inside of a fume hood.
        First, a suitable sample of matrix must be obtained for treatment.
To achieve complete disaggregation of the clay matrix, only matrix
fragments smaller than 1 mm should be treated.  It is recommended that the
bulk sample of the mudstone be first treated with some other disaggregating
medium such as a strong detergent to generate a sample of small rock chips.
Gentle mechanical crushing of the bulk rock is also effective in
generating small chips.  After the initial disaggregation, the bulk sample
should be sieved to collect all disaggregated material smaller than 1 mm in
size.  Washing the sample through a combination of a 1 mm sieve and a sieve
with a mesh smaller than .1 mm will exclude large fragments from the
disaggregated rock while trapping all particles within the desired size
range for treatment.
        Place the sample of sieved mudstone fragments in a flask, beaker,
or other suitable container.  Add 1 part Methyl-Amyl-OH and 4 parts Amine-O
to the sample.  Add approximately 100 parts hot water in a rapid stream to
whip the suspension into a frothy mix.  Adjust the quantities used so that
the volume of sample being treated is equal to approximately 30% of the
volume of the liquid.  I have found that 10 ml of Methyl-Amyl-OH combined
with 40 ml of Amine-O in 500 ml of water will completely dissolve up to 100
grams of mudstone.  After mixing the sample with the reagents, allow the
mixture to stand for several hours.  It is a good idea to occasionally
swirl or stir the mixture to keep the sample from clumping at the bottom of
the container.  After several hours, place the mixture into an ultrasonic
cleaner for 30 minutes to an hour.  Treatment with ultrasound will
completely disaggregate all remaining mudstone pieces.
        Upon completion of the ultrasound treatment the sample should have
the consistency of a thick milkshake.  Wash the solution through a sieve or
series of sieves to collect the insoluble residue left by the treatment.
Incompletely disaggregated samples can be treated a second time if needed.
The residue is now dried and picked for microfossils.  For the
Carboniferous mudstone samples that I have processed, I find that 100 grams
of mudstone will yield between 1 and 10 grams of insoluble residue
consisting primarily of shell fragments and microfossils.

ACKNOWLEDGMENTS
        This research was supported by grants from the Paleontological
Society and Sigma Xi.

REFERENCES
        LUND, R.  1970.  A new technique for chemical preparation of
fossils.   Journal of Paleontology, 44: 578.

J Bret Bennington
Department of Geology
114 Hofstra University
Hempstead, NY 11550-1090
516-463-5568
FAX: 516-463-6010
E-mail: geojbb@vaxc.hofstra.edu