In the latter half of the 20th century, this changed radically: Industrial production had by then increased to the point where the availability of raw materials had become a point of crucial importance. The iconic resource crisis (although this went largely unrecognised at the time) was probably the oil shock following the peak of the Texas oil production.

Yes, though this was more like the last quarter. I tried to find some data on resource prices, but apparently the historical time series are somewhat slippery because the trend they will show depends to a high degree on the deflator (i.e. inflation measure) used.

At least, this is stated by a Swedish Professor called Svedberg. He argues that the inflation indices have been too high, whereas a lot of other people have argued that the changes recently introduced with regard to hedonic pricing have made the indices too low, so I am just passing that along.

Svedberg does have an interesting table in one of his lectures (pdf) which shows that the use of metals and oil has grown at a slower rate than overall economic production since the 1970s. This strongly points to their relative scarcity. With regard to metals, I would guess that recycling rates have gone up a lot, and that the figures shown here are of overall inputs, not extraction.