Princess Pat Mine Afterglow

Afterglow demonstration from the Princess Pat Mine collecting area in San Bernardino County, California. This characteristic is extremely difficult to capture on video. In person the effect lasts for nearly a minute. I’ve run the video at half speed at a certain point to simulate what this looks like. The text announcing this point goes by quickly.

This is short wave under an 18 watt Way Too Cool Lamp. The mineral is willemite, the parent rock undetermined at this time.

November 12, 2019 update: If you look at this video on a big screen TV (Search YouTube for “Thomas Farley Channel” you’ll see the afterglow much better represented. I cut the video off during editing at the point my computer monitor showed no more glow. On a big screen, the glow still has a way to go. I will reshoot and you can then see the results on a TV.

Princess Pat Mine Afterglow from Thomas Farley on Vimeo.

November 13, 2019 update: Here’s the reshot video.

Princess Pat Mine Revised from Thomas Farley on Vimeo.

How long do you see afterglow continuing? On my unadjusted monitors, blackness comes in at twenty seconds, on my standard def TV blackness comes in at around 23 seconds.

I will be adjusting my monitors and possibly my TV to see if I can view the afterglow longer. This site has been recommend for adjusting displays:

That website is difficult to use. My iMac has a native calibration setup process that does not push the length.

In full screen mode using the original HD file, the last spot I see on my iMac is at 25 seconds. Even though I shot this in HD, 3840 x 2160, compression is going on at Vimeo where I uploaded it originally and then published it through Vimeo to YouTube. And I scaled it to 1920*1080 before uploading.


The Princess Pat Mine collecting site is described at this website by Justin Zzyzx who who has written Rockhound Barstow, the best and most current field guide to California’s Mojave.

This specimen was a kind gift from a friend.


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More From the Desert Floor

As a beginning florescent mineral collector I am excited about what I am finding, even if my discoveries are routine for the seasoned vet.

In a recent post I described how happy I was to find a rock with afterglow in an area not written about by collectors. Just last night, though, I discovered something else: one of my rocks fluoresces a different color in different wavelengths.

Normally, a rock or mineral will respond either well or poorly to a certain wavelength. Most materials reacting to shortwave will sit quietly under longwave.  And longwave materials respond weakly to shortwave.

What’s different with this chunky piece of field opal, or something like that, is that it changes colors under different wavelengths. The first photo is visible light, the second shortwave, the third longwave. Some calcite will change into a different color under all wavelengths, that including midwave.

I discovered this change accidentally last night as I was looking over my small group of rocks from my Sunday field trip. In the future I will be sure to check if any rock changes color, not just if it lights up. Multiple wavelength response is something collectors look for and something I will look for, too.

Visible light

Short wave

Long wave


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