Pretty little pearls

Last night we encountered a bit of a mystery on Salmon Creek Beach.  Here are some photos of what we saw, so you can try to come up with a guess yourself.  I'll warn you that this is a bit challenging — we still didn't know for sure until a view through a microscope confirmed our hunch.

The strand line had a distinctly blue-gray hue:

 

When we got down on our hands and knees to take a closer look, this is what we saw:

 

And when I zoomed in close with my camera, we realized there were thousands of small blue-gray objects among the sand grains.  (Many were the same size or smaller than the grains of sand!)

 

 

 

From a distance, they reminded me of "pretty little pearls."  [Given these views from a very small section of the strand line, I can't even imagine how many of these were on the entire beach.]

Any guesses about the identity of these mystery objects?  I'll share the answer tomorrow night.