spe·le·o·them 
(spēlē-ə--=…|th=-ĕm′)
(spēlē-ə--=…|th=-ĕm′)n.
A mineral deposit, such as a stalagmite or stalactite, formed in a cave from the dripping of mineral-rich water.
[Latin spēlaeum, spēlēum, cave (from Greek spēlaion) + Greek thema, thing put down, deposit (from tithenai, to put; see dhē- in the Appendix of Indo-European roots).]