The “Cracked Egg” grain, in which krotite was discovered, is contained in the NWA 1934 Meteorite. Image: Chi Ma |
In an issue of American
Mineralogist, a team of scientists announced the discovery of the new
mineral krotite, one of the earliest minerals formed in our solar system. It is
the main component of an unusual inclusion embedded in a meteorite (NWA 1934),
found in northwest Africa. These objects,
known as refractory inclusions, are thought to be the first planetary materials
formed in our solar system, dating back to before the formation of the Earth
and the other planets.
This particular grain is known affectionately as “Cracked
Egg” for its distinctive appearance. Dr. Harold C. Connolly, Jr. and student
Stuart A. Sweeney Smith at the City Univ. of New York (CUNY) and the American Museum of Natural History (AMNH) first
recognized the grain to be of a very special type, known as a
calcium-aluminum-rich refractory inclusion.
Cracked Egg refractory inclusion was sent to Dr. Chi Ma at
California Institute of Technology (Caltech) for very detailed nano-mineralogy
investigation. Dr. Ma then sent it to Dr. Anthony Kampf, Curator of Mineral
Sciences at the Natural History Museum of Los Angeles County (NHM), for x- ray
diffraction study. Kampf’s findings, confirmed by Ma, showed the main component
of the grain was a low-pressure calcium aluminum oxide (CaAl2O4)
never before found in nature. Kampf’s determination of the atomic arrangement
in the mineral showed it to be the same as that of a man-made component of some
types of refractory (high-temperature) concrete.
What insight can we get from knowing that a common man-made
component of modern concrete is found in nature only as a very rare component
of a grain formed more than 4.5 billion years ago? Such investigations are
essential in deciphering the origins of our solar system. The creation of the
man-made compound requires temperature of at least 1,500°C (2,732°F). This,
coupled with the fact that the compound forms at low pressure, is consistent
with krotite forming as a refractory phase from the solar nebula. Therefore,
the likelihood is that krotite is one of the first minerals formed in our solar
system.
Studies of the unique Cracked Egg refractory inclusion are
continuing, in an effort to learn more about the conditions under which it
formed and subsequently evolved. In addition to krotite, the Cracked Egg
contains at least eight other minerals, including one other mineral new to
science.
