diff --git a/planet/Material.ocg/Coal.ocm b/planet/Material.ocg/Coal.ocm
index 4abc0a816..dff8f67c1 100644
--- a/planet/Material.ocg/Coal.ocm
+++ b/planet/Material.ocg/Coal.ocm
@@ -11,6 +11,7 @@ Dig2ObjectRatio=140
 Blast2ObjectRatio=200
 MaxAirSpeed=100
 MaxSlide=1
+Corrode=50
 Placement=40
 TextureOverlay=coal
 OverlayType=8
diff --git a/planet/Material.ocg/Firestone.ocm b/planet/Material.ocg/Firestone.ocm
index ba0a5d82e..e9cbd6d9c 100644
--- a/planet/Material.ocg/Firestone.ocm
+++ b/planet/Material.ocg/Firestone.ocm
@@ -11,6 +11,7 @@ Blast2Object=Firestone
 Blast2ObjectRatio=115
 MaxAirSpeed=100
 MaxSlide=1
+Corrode=50
 Placement=40
 TextureOverlay=firestone
 Inflammable=1
\ No newline at end of file