Bridgmanite is the most abundant mineral on earth, comprising 38 percent of earth's volume, primarily in the lower mantle at depths below 400 miles (670 km), but was just recently given a name this year.
Bridgmanite is a magnesium iron silicate (Mg,Fe)SiO3 which shows the effect of being shocked by impact as part of a meteorite hitting the earth, as seen in this hand specimen from Australia:
and more pronounced in thin section:
It was named for Percy Bridgman, a Nobel Prize-winning physicist. Before being identified in a meteorite, the mineral was loosely referred to as a silicate perovskite:
By geologic naming convention, a mineral cannot be named until actually examined in hand specimen (hard to do 400 miles deep). So, American researchers looked at a meteorite sample that had fallen in Australia in 1879 as a likely candidate for sampling material similar to this deep mantle mineral. They used a test that involved the use of a micro-focused X-ray beam in conjunction with electron microscopy. And, thus, a mineral was named in the:
In contrast to the shocked appearance of bridgmanite, the strikingly smooth, pearly luster of smithsonite, a zinc carbonate, shows the effect of slow, undisturbed crystal growth:
The crystals often form in grape-like clusters referred to as botryoidal:
Zinc carbonate or zinc spar (ZnCO3) or smithsonite, was named after James Smithson, the same chemist and geologist who donated money for the Smithsonian Institution. Smithsonite has a hardness of 4.5 and a specific gravity of 4.4 - 4.5. In addition to the green, and blue-green colors, it also occurs in lustrous, pearly pink crystals:
Though you may have guessed my favorite, the blue botryoidal, smithsonite clusters:
How about you? Were you shocked to learn bridgmanite was only recently named? That smithsonite occurs in so many pearly, lustrous, botryoidal forms and in so many colors?
Looking forward to your often shocked and shocking comments (as well as your pearly luster),
Steph
