The Collaborative International Dictionary of English v.0.48:

Smalt \Smalt\, n. [It. smalto, LL. smaltum; of Teutonic origin;
   cf. OHG. smalz grease, butter, G. schmalz grease, OHG.
   smelzan to melt, G. schmelzen. See Smelt, v. t., and cf.
   Amel, Enamel.]
   A deep blue pigment or coloring material used in various
   arts. It is a vitreous substance made of cobalt, potash, and
   calcined quartz fused, and reduced to a powder.
   [1913 Webster]