[Illustration: uncaptioned]
The most successful way to split an ironstone concretion is to set it on
edge, long axis horizontal, on any fairly large rock and strike the
upper edge with the hammer. If the concretion is one that developed
around a fossil nucleus, it generally will split along the plane of
weakness, revealing the fossil. Sometimes one side of the concretion
will break off in the middle, in which case the remainder should be
tapped firmly but gently on the upper edge until the fossil is
completely uncovered. Pieces of the broken half should be glued together
neatly with waterproof cement so that the entire specimen can be
retained.
Fossils embedded in shale may be recovered by the same method or by
repeatedly tapping a chisel inserted along the bedding plane. If the
fossil is exposed, the matrix can be chiseled away by slow, painstaking
effort.
The usual method of wrapping plant-bearing nodules is to place the end
of a sheet of newspaper between the two halves of the nodule, fold the
paper over the nodule, and roll it up in the sheet.
[Illustration: How to Wrap a Fossiliferous Concretion]
When several localities are visited in one collecting trip, the fossils
from each should be kept separate; cloth bags are convenient for this
purpose. Notes about the locality should be put in the same bag as
fossils from that locality so that there is no possibility of confusion.
Some fossils are so fragile or porous that they should be covered with a
hardening protective coat of crude gum arabic solution. (Refined gum
arabic will not serve.) This may be applied with a fine brush in
successive layers, or sturdier fossils may be dipped in it.
When a fossil is so delicate that the surface tension of the gum arabic
solution causes the fossil to “spread,” celluloid (not plastic)
dissolved in acetone should be substituted. Before this solution is
used, the specimen must be completely dry or the coating will become
cloudy or opaque.
If the specimen is pyritized, it should be sprayed with lacquer or
shellac to prevent disintegration. If these protective sprays are used
they must be applied to dry specimens during dry weather or the coating
will remain sticky.
[Illustration: uncaptioned]