hal·loy·site 
(hə-loisīt, -zīt)
(hə-loisīt, -zīt)n.
A porcelainlike clay aluminosilicate mineral, Al2SiO5(OH)4·2H2O, consisting of small, slender tubes and formed by the weathering of other aluminosilicate minerals.
[After Jean-Baptiste-Julien d'Omalius d'Halloy (1783-1875), Belgian geologist.]