Yeah galena xtals used to sell in wolworth dime stores for about a
dime way back when I was a kid. Doubt if you could find one
anywhere in the world at this late date. My first hombrew receiver
consisted of a large coil wound on a round oatmeal box, a galena
crystal as detector, an old pair of WW1 headsets that weighed about
10 lbs, and a homebrew slider on the coil so could peak the am
broadcast signals. First you had to use a needle point on the
galena crystal to find a hot spot where the signals produced the
max signal, and then you were all set to lay back and enjoy your
local Radio stations.
Kokomo Joe