Ají de Gallina wrote: “As to Guano, although not “extinct”, it went from mining it 10 meters high in the islands all year round to maybe a couple of months every 7 years”
What is/was guano used for? Which particular animal’s/ species’ guano was Ají de Gallina refering to that was piled 10 meters high? On which islands? … C’mon Aji, don’t be stingy with the info. Share, share! 
I assume that the reference here is to the various islands off the coast of Peru, which were a major source of guano for many decades in the late 19th century. Guano was used as fertiliser, and also as a source of nitrates for several industrial processes, including the manufacture of explosives. The primary source of this guano was seabirds, mostly cormorants, IIRC.
depends on the animal (sea birds or bats) it was a source of sodium or potassium nitrate. either could be made by other methods but this source was easy and cheap. these nitrates could be used eventually in fertilizer or gunpowder.
i guess i had that tab open for a bit and got behind another answer.
Thanks Dervorin and Johnpost for ur quick responses.
Quercus mentioned “urine”: Is s/he referring to good old-fashioned pee? It’s hard to fathom pee being in short supply either.
Ailsite, a type of very hard granite used for curling stones, is very difficult to find now. The island where the granite came from, Ailsa Craig, is off-limits to mineral extraction; only loose rock can be removed Curling stones are now made of granite from Wales, which many curlers feel is inferior to those made from ailsite. Because of the hardness of the stone, though, there are still many ailsite curling stones in common use, and ailsite from loose rock is often used for bottom inserts to curling stones.
Liederkranz cheese is no more.
I understand some forms of ancient wool are not longer available as the breeding stock has degraded. But again, that is animal-based.
Tantalum is apparently in short supply.
Some specific subtypes of coal are becoming quite economically rare (cannel coal, some metallurgical anthracites, some extremely low-sulfur and high-heat content eastern US coal), but not many people care since there are easy and cheap substitutes (in almost all cases).
Blue John is getting rarely IIRC; I know it was quite dear when I last visited the only 2 or 3 mines where it’s found.
And how much woolly mammoth ivory can be left…?
While it’s not inexhaustible, there’s a hell of a lot of permafrost in Siberia, and more tusks are thawed out every year. Forty tons were harvested in 2007. This NY Times article suggests that the remains of 150 million mammoths exist in the upper layers of the permafrost.