Nothing Is Forever: Solution

Each line is the wordplay part of a cryptic clue. Each of the answers is a mineral (sometimes a rock, sometimes a metal) with a letter missing. The minerals are sorted by hardness to aid in solving. The given answer lengths don't count the missing letter.

• Police public relations (5) (cop + pr = copp(e)r)
• Disease initially only infects those exercising (7) (flu + initial letters of "only infects those exercising" = fluo(r)ite)
• Eighty-five percent identify Iowa within Senegal (7) (b + (id + ia) in sn = (o)bsidian)
• Young person around ape (5) (jr surrounding ape = ja(s)per)
• Torch beheaded confused British mother (7) (anagrammed (torch without first letter) + mum = chrom(i)um)
• A hundred run, turning over mud (7) (c + run + revesed mud = c(o)rundum)
• Ruined moai, five hundred on each side (6) (anagrammed moai with d on each side = diamo(n)d)

Taking the missing letters in the given order, we get the answer.

Answer: erosion

Note: This puzzle was intended to be an easy (even compared to the other puzzles) wordplay puzzle. Hopefully the fact that the answers weren't words didn't confuse anyone too much.

Note added on December 31, 2020, for replacement of "Ruined South Pacific statues, five hundred on each side" with "Ruined moai, five hundred on each side": Indirect anagrams are unfair. Replacing this indirect anagram with the thing being anagrammed doesn't hurt the sense of the clue. It makes the puzzle easier but that's not a big issue for the first puzzle.