Did you maybe mean brimstone?
Examples
“And on the far shore a creature that raised its dripping mouth from the rimstone pool and stared into the light with eyes dead white and sightless as the eggs of spiders.”
“Water dripped from stalactites into shallow rimstone pools.”
Lists
These user-created lists contain the word ‘rimstone’.
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An Intermediate Course of Random Pala...
A third uncategorized list of words that catch my eye or fancy. Common or regional names and terms, names of foods and food preparation utensils, bird, plant and animal names, jargon words, and od...
lobscouse, skillygalee, skilly, skippaug, pauhagen, paughaden, poghaden, poggie, pog, skoodle, reef goose, reezle and 138 more...
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the road
glaucoma, tarpaulin, flowstone, flue, rimstone, alabaster, gully, shoring, grike, riprap, windfall, transom and 120 more...
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botello360's list
ruminate, steel, bifurcation, arrivederci, portage, tactile, ruminant, rift, anecdotage, diacritic, cud, hull and 399 more...
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Random
cerograph, calculary, hambeast, canescent, animalculum, atavistic, bloomery, wroth, parturition, obstreperous, sibilant, pourparler and 53 more...
Tweets
Looking for tweets for rimstone.

hernesheir (n): A common variety of speleothem, which is calcite deposited by pooled water into a series of small rims or dams, usually on a cave floor. Jan 15, 2009