Mineral
inclusions tell us about the earlier stages of evolution of
the rock: in metamorphic rocks they can preserve early
fabrics and minerals that have subsequently been
removed from the matrix of the rock by metamorphic
reactions. In lavas, mineral inclusions can be extremely
useful in determining the conditions of equilibration of
the minerals. For example the compositions of plagioclase
inclusions in hornblende can help constrain the pressure
(i.e. depth below the surface) and temperature of the
magma chamber, which could allow the eruptive potential
of the volcano to be estimated.1 In ore bodies, sulphide
melts can be trapped along fractures in quartz; the
cracks subsequently ‘heal’, leaving numerous minute
mineral inclusions distributed along a plane within a
single quartz crystal. The small size of these inclusions
can make it difficult to expose them for analysis, and
their dispersed nature means only a few can be exposed
at a given time.