A root in The Etymologies of the 1930s glossed “glass” with derivatives in both Quenya and Noldorin with the same meaning: ᴹQ. hyelle and N. hele (Ety/KHYEL(ES)). After Tolkien changed Noldorin to Sindarin, he decided that “There was no common Eldarin word for glass”, and that the Sindarin word S. heledh was derived from Khuzdul kheled (PE17/37). Thus the root ᴹ√KHYEL(ES) was abandoned.
Middle Primitive Elvish
sil
root. shine silver
silimā
adjective. silver, shining white
silip
root. SILIP
silimarille
proper name. silimarille
silimē
noun. light of Silpion, †silver
telep
root. silver
kyelep
root. silver
rauta
root. metal
ithil
noun. moon
gilya
noun. star
alkwā
noun. swan
gal
root. shine
kal
root. shine
khyel(es)
root. glass
khyelesē
noun. glass
ranā
proper name. Moon
span
root. white
terēn(ē)
adjective. slender
tinkō
root. metal
The “root” ᴹ√TINKŌ (more likely just a primitive word) appeared in The Etymologies of the 1930s with the gloss “metal” and derivatives like ᴹQ. tinko/N. tinc of the same meaning (Ety/TINKŌ). The reappearance of Q. tinco “metal” in The Lord of the Rings appendices (LotR/1122) strongly indicates its ongoing validity.
ᴹ√TINKŌ may have replaced the root ᴱ√SINI “pale blue” from the Qenya Lexicon of the 1910s with derivatives like ᴱQ. sink “mineral, gem, metal” and G. sinc “metal” (QL/83; GL/67); these early mineral words were originally attributed to ᴱ√SṆT͡YṆ “twinkle” before they were transferred to ᴱ√SINI, leaving only derivatives like ᴱQ. sintl “crystal” and ᴱQ. sinty- “sparkle” under ᴱ√SṆT͡YṆ (QL/85). However, in notes from the late 1960s Tolkien had primitive ✶sinki as an element ✶sinkitamo, the basis for Q. sintamo “smith” (PE17/108). Likewise there is evidence of the earlier root in Q. sinca “flint” as in Q. sincahonda “flint-hearted” (LotR/979), initially given as ᴹQ. tingahondo in Lord of the Rings drafts (SD/68).
Neo-Eldarin: For purposes of Neo-Eldarin, I would definitely use ✶tink- = “metal”, but I think it is worth keeping ✶sinki = “✱mineral = any inorganic solid including both stone and metal” as a variant.
wen-
noun. girl
yel
root. daughter
yen
root. daughter
yend
noun. daughter
A root in The Etymologies of the 1930s, first glossed “copper” and then “metal”, with derivatives ᴹQ. rauta/N. rhaud “metal” and serving mainly to explain names like N. Angrod and N. Finrod (Ety/RAUTĀ). It might have reappeared in the name S. Rodëol “metal of Eöl” from later Silmarillion drafts (WJ/322), but by 1957 Tolkien was explaining the final element of S. Finrod as S. raud “noble” (PE17/49, 118), so I think it is likely that ᴹ√RAUTA “metal” was abandoned.
Neo-Eldarin: For purposes of Neo-Eldarin, I’d use Q. tinco (LotR/1122) and its cognate [N.] tinc (Ety/TINKŌ) for “metal” words. For “copper” I'd use derivatives of √(U)RUS (VT41/10).