[meteorite-list] New Mineral Discovered in NWA 1934 Meteorite (Krotite)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 9 May 2011 12:56:08 -0700 (PDT)
Message-ID: <201105091956.p49Ju88F010658_at_zagami.jpl.nasa.gov>

Contact: Kristin Friedrich
kfriedri at nhm.org
213-763-3532
Natural History Museum of Los Angeles County
May 6, 2011

Paper announces discovery of 1 of earliest minerals formed in solar system

New mineral named krotite, found in meteorite, is described in
American Mineralogist

In the May-June issue of the journal 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 University 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. ("Refractory" refers to the fact that these grains contain
minerals that are stable at very high temperature, which attests to
their likely formation as very primitive, high-temperature condensates
from the solar nebula.)

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.

###

The American Mineralogist paper is entitled "Krotite, CaAl2O4, a new
refractory mineral from the NWA 1934 meteorite." It is authored by Chi
Ma (Caltech), Anthony R. Kampf (NHM), Harold C. Connolly Jr. (CUNY and
AMNH), John R. Beckett (Caltech), George R. Rossman (Caltech), Stuart A.
Sweeney Smith (who was a NSF funded Research for Undergraduate (REU)
student at CUNY/AMNH) and Devin L. Schrader (University of Arizona).
Krotite is named for Alexander N. Krot, a cosmochemist at the University
of Hawaii, in recognition of his significant contributions to the
understanding of early solar system processes.

--------------------------


http://www.hawaii.edu/news/article.php?aId=4415

New mineral, krotite, named after UH Ma-noa researcher

University of Hawai'i at Ma-noa

Contact:
Tara L. Hicks Johnson, (808) 956-3151
Outreach Specialist, School of Ocean and Earth Sciences and Technology

Alexander Krot, (808) 956-3900
Researcher, Hawai`i Institute of Geophysics and Planetology

May 6, 2011

The first natural occurrence of a low-pressure CaAl2O4 mineral has been
found in a refractory inclusion in a carbonaceous chondrite meteorite.
While synthetic low-pressure and high-pressure CaAl2O4 phases are well
known in the field of materials science, only the high-pressure
polymorph had been identified previously in nature (in another
chondrite). Quantitative elemental microanalysis of the new mineral
using the electron microprobe resulted in an empirical formula (based on
four oxygens) of Ca1.02Al1.99O4. It is now officially approved by the
Commission on New Minerals, Nomenclature, and Classification of the
International Mineralogical Association as 'krotite'.

The mineral's name honors Dr. Alexander N. Krot, a University of Hawai'i
at Ma-noa researcher known for his achievements in meteoritics,
especially for studies of the formation of calcium-aluminum-rich
inclusions (CAIs) and chondrules, and his significant contributions to
the understanding of early solar system processes. Krot is also a 2004
recipient of the University of Hawai'i Regents' Medal for Excellence in
Research.

Krotite is the dominant mineral in the central and mantle areas of an
unusual CAI in the NWA 1934 carbonaceous chondrite. The 2.75 mm x 4.5 mm
inclusion is composed mainly of aggregates of krotite crystals, with a
few other calcium-aluminum or magnesium-aluminum oxides and a few
silicates in a thin rim of concentric layers. Cracks, mainly filled with
iron and aluminum hydroxides, crosscut the CAI's rim and parts of its
interior giving it a "cracked egg" appearance. The CAI itself is
surrounded by a matrix of mostly fine-grained olivine.

The discovery team suggests formation in a highly refractory
condensate/evaporative environment in the cooling nebular gas. They say
that the primary mineral assemblage in this CAI was introduced into a
hot gas, which did not melt the CAI but perhaps reacted with surficial
krotite crystals to produce the observed layered rim. The cracks may
have been caused by compaction during accretion of the parent body, but
the meteorite as a whole is essentially unshocked. A final, probably
terrestrial, alteration process most likely filled the cracks with
hydrated oxides during exposure to the northwest African environment.
This CAI, along with its new mineral, krotite, will be the subject of
additional research to determine formation and cosmochemical details.
Because CAIs were the first solids formed in the solar nebula about 4.6
billion years ago, they help cosmochemists piece together records of
nebular and early solar system processes and how the first solid
building blocks eventually turned into asteroids and planets.

For more information, visit: Discovery of New Mineral, Krotite, in a
CAI - http://www.psrd.hawaii.edu/CosmoSparks/May11/krotite.html or

Dating the Earliest Solids in our Solar System
http://www.psrd.hawaiii.edu/Sept02/isotopicAges.html
Received on Mon 09 May 2011 03:56:08 PM PDT