Olivinbomb (16.690 g)
A volcanic bomb is a ballistic pyroclastite ejected during a volcanic eruption., i.e. a fragment of lava or rocks (lava fragments mixed with the remains of the vent filling or venting) that are ejected through the air during volcanic eruptions before settling. The bomb has rounded shapes; the outer shape and surface show signs that the pyroclast had melted during formation and transport. In older literature, every pyroclast ejected on a ballistic path is considered a bomb.
Volcanism not only transports magma, but also occasionally fragments of the Earth's mantle to the Earth's surface. These mantle fragments are coarse-grained rocks consisting essentially of olivine, orthopyroxene, clinopyroxene and spinel or garnet. Such rocks are commonly referred to as mantle peridotites The solid (but not rigid) mantle of the earth may have melted to about 1 % in the asthenosphere (about 100-200 km depth). However, most magmas are formed at shallower depths. In order to clarify the formation of rock melts (magma), it is necessary to know the composition of the earth's mantle, or the origin of most magmas.