Isn't that cool?
They are porous like pumice but seem to be sealed with some sort of waxy resin. It's also polished to a smooth surface.
When I saw these, I knew immediately they must be paired with irregular large white pearls and strung on black silk.
The problem with the irregular surface of the lava is that some holes were bigger on some than others, so they wouldn't be stopped from sliding by the knot on the silk, so I happened to see a nearby strand of faceted quartz beads which I just used as spacers to stop the lava from sliding.
The clasp I bought at a lovely bead shop in London near Covent Garden about 8 years ago. This is the best bead store I've ever seen. I have a few other findings I've hoarded from one of those shopping trips, but they won't last forever.
I'm going to keep this necklace and wear it. I can't remember the last time I made myself a piece of jewelry, but it's been years. I'm concerned about how easily the lava beads may fray/cut the cord. If they are tight enough that they won't slide, then it won't matter. I definitely don't want to sell something like this to anyone until i know it won't fall apart easily.