  The gamma-ray activities of 33 meteorite samples (30 ordinary chondrites, 1
Mars meteorite, 1 iron, 1 howardite) collected during Omani-Swiss meteorite
search campaigns 2001-2008 were nondestructively measured using an ultra-low
background gamma-ray detector. The results provide several types of
information: Potassium and thorium concentrations were found to range within
typical values for the meteorite types. Similar mean 26Al activities in groups
of ordinary chondrites with a) weathering degrees W0-1 and low 14C terrestrial
age and b) weathering degree W3-4 and high 14C terrestrial age are mostly
consistent with activities observed in recent falls. The older group shows no
significant depletion in 26Al. Among the least weathered samples one meteorite
(SaU 424) was found to contain detectable 22Na identifying it as recent fall
close to the year 2000. Based on an estimate of the surface area searched, the
corresponding fall rate is ~120 events/106 km2*a, consistent with other
estimations. Twelve samples from the large JaH 091 strewn field (total mass
~4.5 t) show significant variations of 26Al activities, including the highest
values measured, consistent with a meteoroid radius of ~115 cm. Activities of
238U daughter elements demonstrate terrestrial contamination with 226Ra and
possible loss of 222Rn. Recent contamination with small amounts of 137Cs is
ubiquitous. We conclude that gamma-ray spectroscopy of a selection of
meteorites with low degrees of weathering is particularly useful to detect
recent falls among meteorites collected in hot deserts.
