The Collaborative International Dictionary
Lumachel
Lumachel \Lu"ma*chel\, Lumachella \Lu`ma*chel"la\, n. [F. lumachelle, It. lumachella, fr. lamachella a little snail, dim. of lumaca a snail, fr. L. limax, -acis.] (Min.) A grayish brown limestone, containing fossil shells, which reflect a beautiful play of colors. It is also called fire marble, from its fiery reflections.
Wiktionary
lumachel
n. (context mineralogy English) A grey form of limestone that contains fossil shells, and reflects a fiery play of colours