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Met Name

Met Type

Thin Sections

1.3 gram fragment.   Aubrite

TKW 1.1 tons (1000 kg). Observed fall February 18, 1948, near Norton, Kansas, USA.

 

Steve writes:

In honor of America's birthday, I told Paul I could do a 4th of July submission that showed red fluorescence of a white U.S. meteorite with blue UV reflections (alright, more like magenta, white, and purplish-blue, but hopefully close enough!). So with that introduction, I humbly offer this example of the Norton County meteorite. (And my apologies to Paul's audience from other countries that might not get the red, white, and blue reference.)

Norton County is a well-known aubrite that has already appeared on a half dozen wonderful MPODs. The piece in this submission doesn't add anything by way of size or obviously unique features, but since not a lot of people I've talked to are aware of it, I thought it would be fun to share some examples of Norton County's fluorescence.

Aubrites are principally composed of enstatite, but that mineral in Norton County contains much less iron, making it white as compared to the green to brown or even almost dark gray colors of some of the other aubrites. The even lower iron content crystals fluoresce under shortwave UV but under normal light are hard to differentiate from the adjacent non-fluorescing enstatite.

To illustrate this phenomenon, the animated gif in Photo 1 shows a 1.3 gram Norton County fragment under both normal white and shortwave UV lights (for reference, the diameter of the pedestal is one inch). The photo setup was a bit difficult to implement with the equipment I have and as a consequence the angles of these lights were necessarily different, but the effect is nonetheless still evident. The purplish-blue illumination was not visible to the naked eye, but to the camera's 15 second exposures the effect is likely similar to the non-fluorescent reflections often seen when using long wave UV light. Over the small fluorescent areas of this piece, this pervasive purplish-blue glow tended to make the naturally yellowish-orange fluorescence appear magenta in the long exposures.

As an aside, Norton County is my only aubrite, and none of my other 300 or so meteorites fluoresce. In fact only five of my eighteen pieces of that meteorite do, possibly suggesting that even in Norton County, the fluorescing minerals are somewhat rare. Similarly, a couple of years ago I was at Bob Falls' house and out of curiosity tested a large slice of his Pena Blanca Springs aubrite. A handful of very small areas did fluoresce, possibly indicating that this phenomenon - though sparse when present - is a common attribute of aubrites that exhibit white enstatite. I also have a Cumberland Falls thin section that I wanted to check, but like my Norton County thin section, it's glass also has hazing problems.