Gamma Spectrometry Forum

A spectrum from Apatite.

A local charms and trinkets shop in West Hampstead London also sells ‘healing’ stones that give off ‘energy’. I believe the proprietor to be sincere in her claims and have no wish to be snide about her beliefs but I was more curious about the tangible properties of the gemstones that I could relate to so I took out my PDS-100 and asked her if I could scan them. The background level in the shop was slightly elevated and in no time I found the source to be small collection of Apatite stones. Putting the detector directly on the stones raise the count from about 20 to 80+ cps. I wanted to find out more regards their origin but I was having difficulty explaining what was going on, the proprietor who had no grasp of basic physics, seemed to getting more nervous the more I tried to explain. So I just bought a handful and took them home. The unshielded background for my CsI detector is 120 cps, shielding reduces this to 7cps. The 5 or 6 Apatite stones that fit comfortably in my palm (under shielding) gave 170+ cps.

Here is the spectrum I obtained - energy summed. I am very inexperienced at this I think this is a signal example of a Thorium Series.

well..the desciption is spot on: "stimulates creativity and helps align higher knowledge"!

about your spectrum: the bump you label K-40 - isn't that the double escape peak? (2614-1022)?

Hello Ipelupessy, Thanks. Yes looking at the original data - I think I mislabelled and meant to apply 'k-40,' to the peak immediately to the left. I think the peak I labelled k-40 is Ac-228 at 1588 KeV, and I see Bi-212 broadcasts on 1620 KeV and Ac-228 on 1630 KeV too, may be they are mixed in there as well?. PRA said Gaussian for the the actual k-40 peak to the left was 1454 KeV (sd 20) and the mislabelled peak has a mean of 1609 KeV (sd 29). That was the with the original calibration using the extreme ends of Ba-133 and Na-22. I later re-calibrated using known Th peaks and got a better fit but I forgot to save that result - may be I'll do it again this weekend and get a better number for the mislabelled peak. And perhaps the unlabelled peak just around 2100 KeV in my new calibration above is the double escape peak?