I forgot about mineral (including but not limited to glass, gemstone, crystal,
hematite, jade, onyx, howlite, jasper, granite, quartz, carborundum),
synthetic (including epoxy, bakelite, resorcinol glue), clay, putty, leather,
pressed rose petal, cellulose, carved bone, ivory, seashell, pearl.....
-- all of which are solid.