A word in Declension of Nouns from the early 1930s glossed “grit” with various forms representing the inflections of nouns with lost ancient vowels: malǝ- (PE21/19, 24). It may be a later iteration of ᴱQ. mar (mard-) “grit, course grain or powder” from the Qenya Lexicon of the 1910s, a derivative of the root ᴱ√MṚŘṚ [MṚÐṚ] “grind” (QL/63). Later still Tolkien gave the primitive form ✶smalŭ with the gloss “dust, grit” in Common Eldarin: Noun Structure (EVS2) from the early 1950s, though this primitive form had no derivatives.
Neo-Eldarin: For purposes of Neo-Eldarin, I prefer to use ᴹ✶smalu with its 1930s sense “pollen, yellow powder”, as this form has derivatives in The Etymologies (Ety/SMAL), and its root meaning ᴹ√SMAL “yellow” is a better match to the later root √MAL “yellow, gold”. I think it is possible to retain ᴹQ. mál “grit”, however, by assuming that it is a derivative of ᴹ√MBAL “✱pound”, which is a better match with 1910s ᴱQ. mar < ᴱ√MṚÐṚ “grind”.