**5. Mineralogy of Kone silicic eruptives**

Kone volcano is predominantly rhyolite in composition with minor trachyte [13]. The majority of kone eruptive rocks are phenocryst-poor with total modal contents of <6%. Given the textural diversity of Kone silicic volcanics (lava, ignimbrite and pumice) we have only selected samples from the first phase (lava) and second phase (ignimbrite) eruptives to illustrate the mineralogy of the silicic melt. The dominant mineral assemblage, with decreasing order of abundance, is alkali feldspar, quartz, clinopyroxene, aenigmatite and olivine, accompanied by rare Fe-Ti oxides and apatite.

Alkali feldspar is overwhelmingly the most abundant phenocryst and forms tabular crystals. Most of the crystals are fragmented. Quartz occurs as rounded microphenocrysts. Clinopyroxene forms euhedral to subhedral pale green crystals. The Na-Fe-Ti silicate aenigmatite is a distinctive phenocryst constituent, recognized by its blood-red to black pleochroism. Olivine occurs as colorless, partly resorbed grains. Fe-Ti oxides form discrete equant crystals, but more commonly occur as inclusions within clinopyroxene. Small euhedral apatite prisms are a common accessory mineral. Quartz and alkali feldspar are common groundmass phases.


### **Table 1.**

*Composition of alkali feldspar from Kone silicic eruptives.*
