diff --git a/OpenRa.Game/Game.cs b/OpenRa.Game/Game.cs
index cb2e3fed1b..22631abbf8 100644
--- a/OpenRa.Game/Game.cs
+++ b/OpenRa.Game/Game.cs
@@ -100,7 +100,7 @@ namespace OpenRa.Game
 
 			chrome = new Chrome(renderer);
 
-			oreFrequency = (int)(Rules.General.GrowthRate * 60 * 1000);
+			oreFrequency = (int)(Rules.General.GrowthRate * 60 * 25);
 			oreTicks = oreFrequency;
 		}
 
@@ -182,11 +182,12 @@ namespace OpenRa.Game
 							controller.orderGenerator.Tick();
 
 						if (--oreTicks == 0)
-						{
 							using (new PerfSample("ore"))
+							{
 								Rules.Map.GrowOre(SharedRandom);
-							oreTicks = oreFrequency;
-						}
+								minimap.InvalidateOre();
+								oreTicks = oreFrequency;
+							}
 
 						world.Tick();
 						UnitInfluence.Tick();
diff --git a/OpenRa.Game/Graphics/Minimap.cs b/OpenRa.Game/Graphics/Minimap.cs
index 21031eb6e5..fbb13f3ef9 100644
--- a/OpenRa.Game/Graphics/Minimap.cs
+++ b/OpenRa.Game/Graphics/Minimap.cs
@@ -10,7 +10,7 @@ namespace OpenRa.Game.Graphics
 		Sheet sheet;
 		SpriteRenderer spriteRenderer;
 		Sprite sprite;
-		Bitmap terrain;
+		Bitmap terrain, oreLayer;
 
 		public void Tick() { }
 
@@ -24,6 +24,8 @@ namespace OpenRa.Game.Graphics
 		// todo: extract these from the palette
 		Color[] terrainTypeColors;
 
+		public void InvalidateOre() { oreLayer = null; }
+
 		public void Update()
 		{
 			if (terrainTypeColors == null)
@@ -39,8 +41,10 @@ namespace OpenRa.Game.Graphics
 					pal.GetColor(0x1f),
 					pal.GetColor(0x68),
 					pal.GetColor(0x6b),
+					pal.GetColor(0x6d),
 				};
 			}
+			
 			if (terrain == null)
 			{
 				terrain = new Bitmap(128, 128);
@@ -51,7 +55,16 @@ namespace OpenRa.Game.Graphics
 							: Color.Black);
 			}
 
-			var bitmap = new Bitmap(terrain);
+			if (oreLayer == null)
+			{
+				oreLayer = new Bitmap(terrain);
+				for (var y = 0; y < 128; y++)
+					for (var x = 0; x < 128; x++)
+						if (Rules.Map.ContainsResource(new int2(x, y)))
+						oreLayer.SetPixel(x, y, terrainTypeColors[(int)TerrainMovementType.Ore]);
+			}
+
+			var bitmap = new Bitmap(oreLayer);
 			
 			for( var y = 0; y < 128; y++ )
 				for (var x = 0; x < 128; x++)