"Hot Rocks" Cause Injury, Mystery

As reported on Yahoo / GMA (video), and by the ever-vigilant Jyllian Kemsley over at Safety Zone, a real-life chemical mystery is unfolding. A few days ago, a California couple strolled the beach with their kids, and pocketed a few interesting-looking rocks they had found. Later that evening, the rocks caught fire while in Lyn Hiner's pants pocket, with a "...bright, intense flame," that, according to reports, couldn't be patted or smothered out. The resulting fire hospitalized both wife and husband with severe burns.

Source: AP

So, the question remains: what was on the rocks? The orange substance, found on green and gray surfaces, may indeed be "phosphorous" [sic], as mentioned by a mildly chemophobic (nearby nuclear plant, firing range?!) Associated Press report. A local geologist commented that the orange coloration is "...not natural, it's human made." With some imagination, you could probably come up with a few phosphorus alternatives (looking at you here, ExploSci!).

Pyrophoric Metals - Finely dispersed powders of magnesium, zinc, or thermite could certainly react with a little acid or moisture. However, these don't fit the bill as "orange substances."


Flash powder - Often used in special effects and flares. This blend of oxidizers and reactive metals would have to have been intentionally placed on the rocks, since they wouldn't have remained stable for long, out in the open air.


Reactive Groups - Many organic groups react with violent decomposition or exotherms when sparked, touched, or heated. Although certainly far-fetched, someone fooling around with picrates, nitrates, or perchlorates could have inadvertently doped the stones in question. There's at least a few dozen of these salts around, and many (iron perchlorate, mercury fulminate, ammonium picrate) may actually be orange or yellow-colored.