Add new pumice material

- Flowing lava quenches to pumice
- Pumice can spontaneously melt back to flowing
  lava, when touching lava, and sometimes even
  when still quenched.
- Pumice cannot be harvested or moved, it's
  utterly destroyed by digging.

mods/nc_api/util_sound.lua

@@ -67,12 +67,13 @@ local gains_base = {
 	place_failed = 0.2,
 	fall = 0.1
 }
-function nodecore.sounds(name, gains)
+function nodecore.sounds(name, gains, pitch)
 	local t = {}
 	for k, v in pairs(gains_base) do
 		t[k] = {
 			name = name,
-			gain = (gains and gains[k] or 1) * v
+			gain = (gains and gains[k] or 1) * v,
+			pitch = pitch
 		}
 	end
 	return t

mods/nc_igneous/init.lua

@@ -6,3 +6,4 @@ local include, nodecore
 nodecore.amcoremod()
 
 include('amalgam')
+include('pumice')

mods/nc_igneous/pumice.lua

@@ -0,0 +1,63 @@
+-- LUALOCALS < ---------------------------------------------------------
+local math, minetest, nodecore
+    = math, minetest, nodecore
+local math_random
+    = math.random
+-- LUALOCALS > ---------------------------------------------------------
+
+local modname = minetest.get_current_modname()
+
+local pumname = modname .. ":pumice"
+
+local pumdef
+pumdef = {
+	description = "Pumice",
+	tiles = {"nc_igneous_pumice.png"},
+	groups = {
+		cracky = 2,
+		stack_as_node = 1
+	},
+	drop = "",
+	silktouch = false,
+	after_dig_node = function(pos)
+		nodecore.digparticles(pumdef, {
+				time = 0.05,
+				amount = 100,
+				minpos = {x = pos.x - 0.5, y = pos.y - 0.5, z = pos.z - 0.5},
+				maxpos = {x = pos.x + 0.5, y = pos.y + 0.5, z = pos.z + 0.5},
+				minvel = {x = -2, y = -2, z = -2},
+				maxvel = {x = 2, y = 2, z = 2},
+				minacc = {x = 0, y = -4, z = 0},
+				maxacc = {x = 0, y = -4, z = 0},
+				minexptime = 0.25,
+				maxexptime = 0.5,
+				minsize = 1,
+				maxsize = 8
+			})
+	end,
+	sounds = nodecore.sounds("nc_optics_glassy", nil, 0.8),
+}
+minetest.register_node(pumname, pumdef)
+
+nodecore.register_limited_abm({
+		label = "Quench Lava to Pumice",
+		interval = 1,
+		chance = 2,
+		nodenames = {"nc_terrain:lava_flowing"},
+		neighbors = {"group:coolant"},
+		action = function(pos)
+			return nodecore.set_loud(pos, {name = pumname})
+		end
+	})
+
+nodecore.register_limited_abm({
+		label = "Melt Pumice",
+		interval = 1,
+		chance = 2,
+		nodenames = {pumname},
+		neighbors = {"group:lava"},
+		action = function(pos)
+			if math_random() < 0.95 and nodecore.quenched(pos) then return end
+			return nodecore.set_loud(pos, {name = "nc_terrain:lava_flowing", param2 = 7})
+		end
+	})