Hi sheila
When I teach pearls, I include some shells I have collected. I have a mussel shell, a
pinctada maxima with a gold lip (that was given to me as a set of salad plates!), an akoya shell and an ordinary oyster shell. I would use more if I had them. I take along a small gorgeous abalone shell too. Most have seen abalone shells, few know they are pearl-bearing mollusks, too. I also have a large conch shell- come to think of it. I think I'll take next time as an example of a non-nacreous pearl shell.
I like to start with asking the question, "Where do pearls come from". someone, if not several people, will say, "Oysters!" so I show them the oyster shell, which they all recognize and explain that is is a non-nacreous shell of a kind that does not produce pearls and show how it is far removed in looks from the pearl producing mollusks, which aren't true oysters at all. Then I show the rest of the shells explaining what nacre is and how it manifests in a variety of sea shells and freshwater mussel shells, which are very pretty (and useful) shells.
If you are going to do this more than once, you might want to put together one of each of many kinds of colors and shapes of pearls as V101 has mentioned, above. I knew someone who put many kinds of examples all on one strand and called it a "teaching" strand, which it certainly would be. Many kinds of pearls can be addd to such as strand, such as eamples of pearls with orient, luster and water, the last of which is not common, even in the best pearls. Treated and untreated pearls make a great topic, and geat examples on a teaching strand because most people including jewelers) do not know how much treatment (artifical enhancement) their pearls have had. That knowledge is often surprising for people to hear.
Hope this is helpful to you and/or other folks "talkin' pearl"!
You know, folks who work with loose pearls and or beads often keep one or more of each pearl with its reorder info in little thunbnail size- plastic bags with labels. This is good for storage, bad for teaching. I am trying to think of a way to make each pearl easily detachable from a strand. What comes to mind is to put each teaching pearl on its own piece of thread with a tag that labels it and tie it into a loop that is easily moved on and off another "mother" thread. I had a flash of having a piece of chain and putting a lobster clasp on each individual pearl's thread and hook it onto the chain, or maybe to a board.
A board with the labels and info written on the board and its own example tied to each label, might be a another way to present and oganize material.
If these aren't the kind of ideas you had in mind, please forgive an old lady
and lowly beader
who is just sitting here and thinking what I would do.