Hi, I'm Callan with the Perot Museum of
Nature and Science. Let's make some salty
fossils today. But first, let's consider
is this a fossil? Nope, it's just a
chicken bone. It's a bleached and clean
chicken bone. Bones are amazing because
they're strong and they support us, but
given time, they still decay. Something
that can preserve at least part of a
bone for a longer period of time is the
process of fossilization. If a bone is
going to fossilize, one way this can
happen is if the molecules that might be
long and complex. The organic molecules
for example, may be collagen. Given time,
those typically would decay. But what if
we could replace those molecules with
something where a single unit was a
little simpler? Maybe only two atoms like
a mineral, for example. Given time, this
type of molecule can survive. One example
is NaCl sodium chloride. And that's what
we'll use today. You will need a few
things to make these salty fossils.
You'll need scissors. A sponge that
you're going to cut into whatever shape
you'd like. Salt. Here, I'm using Epsom
salt, but you can try this with table
salt. Water. Sand -- you can try this with
dirt if you don't have sand. You'll see I
try it with both later on. As well as a
container for all these things. The first
thing you'll do, of course, is take your
scissors and cut that sponge into the
shape you'd like for your fossils. Then
you're going to make a super saturated
salt solution by adding some salt into a
pot of warm water. You want the amount of
salt in this pot to be enough that
they're still undissolved salt at the
bottom of the liquid. After that, you're
going to soak your pre-made sponge in
this salt water bath, making sure they're
nice and saturated .Move your sponge over
your container and then add sand to it
until your sand is fully covering the
sponge like this. Now is the time for you
to add your warm salty water. You're
going to add this until it is covering
the sand. Just a little bit on top of
that sand. And it might spill and that's
okay.
Now you'll need to set this aside.
Probably for at least a week until it's
dry. Okay, so it's been about a week and
here's what I have. The salt is pretty
soft, so this is going to be softer than
most fossils
actually would be. Probably have some
delicate tools over here for excavating
as well as a paper towel so I hopefully
don't make too much of a mess. I want to
remove as much extra material as
possible without damaging my fossilized
sponge, so I'm being very gentle all the
way through this process, trying to clean
off the matrix fairly well. You can see
for the one that I did in the dirt it's
still pretty dirty. It's also fairly soft
where the one that came out of the sand.
My Stegosaurus over here.
You can see they're still probably
some salt matrix. Meaning, it wouldn't
actually be part of my fossil. It's just
clinging on to the fossil. But I'm not a
good enough preparator to get that removed.
It's hard to see which is the matrix or
the sand. In this case on the outside. So
let's cut them open. Both my t-rex and my
Stegosaurus you can see the center of
the sponge is not crystallized. However,
around the edge of each there is a layer
of salt crystals which might be a little
hard to see. It'd be interesting to play
around with the conditions of this
experiment to see if we could get the
middle part of this sponge to
crystallize. Even better, bones aren't the
only thing that forms. In this way here I
do have an actual fossil this is a
trilobite.
So in this case, the minerals didn't
replace bone, but they replaced the
exoskeleton of the trilobite itself. Can
you think of any other fossils where
they would form like this? Is there any
other material that can form by
permineralization, as in are there any other
types of fossils? We do have some more
resources on our website if you'd like
to do an activity about trace fossils,
for example. And as always, thanks for
joining us today. Bye!
