Rotem, Dilsen-Stokkem, Limburg Province, Belgium

How old are these dumps? I am wondering how long it takes for some of these minerals to form in a slag pile.

I too am very curious about the speed of formation of secondary minerals in slags. Slags exposed to seawater in Tacoma, Washington state, for about 100 years are well known for their secondary minerals. On roughly 70 year old slags exposed to seawater in Japan I've found material looking quite similar to the Rotem material. Anyone have examples of faster growth?

Climate (temperature and humidity) are probably decisive.

The zinc-factory S.A. de Rothem produced between 1913 and 1967 (source: [www.utersjank.be]). I have visited the site numerous times to collect the slag minerals, but I don't know how old the slags were on each of the different spots in the area. The process by which the Zinc was produced at Rothem is described in detail (in Dutch) in Fruytier M. (2003): Dilsen-Stokkem, een nieuwe vindplaats en nu bijna verdwenen! Nautilus 2003, 3, 93-118.
Cheers, Frank

Then it would seem the secondary minerals must be between 45 < 99 years old?

Good to know, I thought it might take longer. I was looking through a 100 year old copper slag pile and couldn't find anything of interest, I thought maybe it wasn't old enough but I guess there just isn't anything to be found.

Is the pile well-drained, Reiner? I guess availability of water would be critical? (in which case you might want to dig into the bottom of the pile, where it's in contact with the soil under it)

Hello Alfredo,

Good point, it is well drained, I will have to do some digging maybe I will get lucky.