Jep, it's the so-called "Glasmine 43", a perfidious anti-personnel mine, which could not be detected with conventional detectors, because these devices responded to metal...:
The first examples had a conventional lever igniter installed...:
...which was relatively easy to defuse (if you tracked down the mine!) - the later (and most) of these things were equipped from 1944 with chemical detonators whose reactants consisted of a liquid and a reactive powder. In this detonator, the combination of the substances led to an explosive reaction. The explosive charge consisted of 200 grams of pincric acid.
If the lid was removed to defuse the alleged lever detonator, a barely visible plate installed under the lid broke, the chemical detonator activated - and WUMMS!
The Germans produced 11 million of them, at the end of the war there were still 9.5 million in the arsenals, which were either destroyed or found their way to other theatres of war.
For example, FARC guerrillas in Colombia were supposed to have used glass mines of the ex-Wehrmacht in the 90s.
The Red Army equivalent to the German glass mine was the wooden "PMB 6", also not to be located with detectors...:
Cheers