Volcanic ash deposits composed of mafic minerals sometimes develop a very distinctive reddish-orange color after weathering at the surface. This coloration results from the

The reddish-orange colour of weathering of volcanic ash is most likely due to its iron sulfide content which oxidizes to iron oxide so that limonite is yellow and hematite is red and in ash since it is such fine grained material it weathers more rapidly because it has a large surface area.