"Help Scientist" Surface Feature Mission

[Morbidous]

I'm not sure of the exact requirements but I can't get a mission objective to complete.

It is a "Help a Scientist" mission to a waypoint on Minmus. I need a Materials Study, Seismic Scan, and Green Sandstone Analysis. The first two work ok, but the Green Sandstone Analysis does not. First, finding a Green Sandstone within range of the waypoint feels like it might be up to blind chance. Finding one just a few meters outside of the radius of the waypoint does not work. But eventually upon finding one within the radius, it still did not work.

Note that this is for picking it up by hand, rather than using a scanner arm. I don't think that should matter, since it just asks for a "Green Sandstone Analysis" which I'm definitely doing. The issue could be that the mission says "Situation: Landed", which might mean that you cannot perform the experiment on foot.

This all may be by design, I'm not sure. At least the mission text could be more clear about how exactly to complete this kind of mission.

UPDATE: tried again with a scanner arm and still wouldn't complete. I was landed, within the waypoint, and was definitely completing a "Green Sandstone Analysis" experiment, so I don't think I'm missing anything.