I think this occurs only with blocks being placed from the offhand, need to verify. No crash occurs, just console output. Everything functions correctly.

[13:51:38] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:666) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:385) [lb.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:611) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:469) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_91]
Caused by: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at net.silentchaos512.gems.util.ToolHelper.onItemUse(ToolHelper.java:424) ~[ToolHelper.class:?]
at net.silentchaos512.gems.item.tool.ItemGemPickaxe.func_180614_a(ItemGemPickaxe.java:133) ~[ItemGemPickaxe.class:?]
at net.minecraftforge.common.ForgeHooks.onPlaceItemIntoWorld(ForgeHooks.java:735) ~[ForgeHooks.class:?]
at net.minecraft.item.ItemStack.func_179546_a(ItemStack.java:142) ~[adq.class:?]
at net.minecraft.server.management.PlayerInteractionManager.func_187251_a(PlayerInteractionManager.java:484) ~[lt.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_184337_a(NetHandlerPlayServer.java:680) ~[mc.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:55) ~[jh.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:11) ~[jh.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fj$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:45) ~[h.class:?]
... 5 more
[13:51:38] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:666) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:385) [lb.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:611) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:469) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_91]
Caused by: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at net.silentchaos512.gems.util.ToolHelper.onItemUse(ToolHelper.java:424) ~[ToolHelper.class:?]
at net.silentchaos512.gems.item.tool.ItemGemPickaxe.func_180614_a(ItemGemPickaxe.java:133) ~[ItemGemPickaxe.class:?]
at net.minecraftforge.common.ForgeHooks.onPlaceItemIntoWorld(ForgeHooks.java:735) ~[ForgeHooks.class:?]
at net.minecraft.item.ItemStack.func_179546_a(ItemStack.java:142) ~[adq.class:?]
at net.minecraft.server.management.PlayerInteractionManager.func_187251_a(PlayerInteractionManager.java:484) ~[lt.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_184337_a(NetHandlerPlayServer.java:680) ~[mc.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:55) ~[jh.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:11) ~[jh.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fj$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:45) ~[h.class:?]
... 5 more
[13:51:40] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:666) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:385) [lb.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:611) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:469) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_91]
Caused by: java.lang.NoSuchMethodError: net.minecraft.item.ItemBlock.func_179222_a(Lnet/minecraft/world/World;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/util/EnumFacing;Lnet/minecraft/entity/player/EntityPlayer;Lnet/minecraft/item/ItemStack;)Z
at net.silentchaos512.gems.util.ToolHelper.onItemUse(ToolHelper.java:424) ~[ToolHelper.class:?]
at net.silentchaos512.gems.item.tool.ItemGemPickaxe.func_180614_a(ItemGemPickaxe.java:133) ~[ItemGemPickaxe.class:?]
at net.minecraftforge.common.ForgeHooks.onPlaceItemIntoWorld(ForgeHooks.java:735) ~[ForgeHooks.class:?]
at net.minecraft.item.ItemStack.func_179546_a(ItemStack.java:142) ~[adq.class:?]
at net.minecraft.server.management.PlayerInteractionManager.func_187251_a(PlayerInteractionManager.java:484) ~[lt.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_184337_a(NetHandlerPlayServer.java:680) ~[mc.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:55) ~[jh.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.func_148833_a(SourceFile:11) ~[jh.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fj$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_91]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_91]
at net.minecraft.util.Util.func_181617_a(SourceFile:45) ~[h.class:?]
... 5 more