coaldust = new coaldust().setUnlocalizedName("coaldust").setTextureName("al:coaldust").setCreativeTab(tabAlchimia);
add these methods in the constructor instead.
you are not registering your textures try this...
if (event.getSide() == Side.CLIENT) {
regTexture(blockSau);
}
public void regTexture(Item item) {
Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register(item, 0, new ModelResourceLocation(MODID + ":" + item.getUnlocalizedName().substring(5), "inventory"));
}