nodes aren't ground content (#26)

nodes.lua

@@ -5,7 +5,7 @@ local chains_sbox = {type = "fixed",fixed = { -0.1, -0.5, -0.1, 0.1, 0.5, 0.1 }}
 minetest.register_node("basic_materials:cement_block", {
 	description = S("Cement"),
 	tiles = {"basic_materials_cement_block.png"},
-	is_ground_content = true,
+	is_ground_content = false,
 	groups = {cracky=2, dig_stone = 1, pickaxey=5},
 	_mcl_hardness=1.6,
 	sounds = sound_api.node_sound_stone_defaults(),
@@ -14,6 +14,7 @@ minetest.register_node("basic_materials:cement_block", {
 minetest.register_node("basic_materials:concrete_block", {
 	description = S("Concrete Block"),
 	tiles = {"basic_materials_concrete_block.png",},
+	is_ground_content = false,
 	groups = {cracky=1, concrete=1, dig_stone = 1, pickaxey=5},
 	_mcl_hardness=1.6,
 	sounds = sound_api.node_sound_stone_defaults(),
@@ -29,6 +30,7 @@ minetest.register_node("basic_materials:chain_steel", {
 	sunlight_propagates = true,
 	paramtype = "light",
 	inventory_image = "basic_materials_chain_steel_inv.png",
+	is_ground_content = false,
 	groups = {cracky=3, dig_stone = 1, pickaxey=5},
 	_mcl_hardness=1.6,
 	selection_box = chains_sbox,
@@ -44,6 +46,7 @@ minetest.register_node("basic_materials:chain_brass", {
 	sunlight_propagates = true,
 	paramtype = "light",
 	inventory_image = "basic_materials_chain_brass_inv.png",
+	is_ground_content = false,
 	groups = {cracky=3, dig_stone = 1, pickaxey=5},
 	_mcl_hardness=1.6,
 	selection_box = chains_sbox,