The mineralogy throughout Merapi’s history is generally very similar, and the characteristic assemblage is plagioclase, clinopyroxene (augite–salite), brown hornblende, olivine, titanomagnetite, and hypersthene (only in basaltic andesites), embed in a clear to brown glassy matrix (Camus et al, 2000). The main accessory minerals are apatite, which occur as microphenocrysts, alkali-feldspar and tridymite as interstitial phases in the groundmass. The groundmass is partly crystalline, with mainly microlites of plagioclase and pyroxenes.