ClusterRenderer.cs

        //Draw a single marker
        protected override void OnBeforeClusterItemRendered(Java.Lang.Object p0, MarkerOptions markerOptions)
        {
            //Icon for single marker
            markerOptions.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.marker));

            //Text for Info Window
            markerOptions.SetTitle("Grenoble");
            markerOptions.SetSnippet(markerOptions.Position.Latitude.ToString() + ", " + markerOptions.Position.Longitude.ToString());
        }