Do you have any Rock Monsters in your LEGO® collection from the old Rock Raiders theme from 1999? If so, you already have one of the only official randomized color elements that appeared in a standard LEGO® set!
Every Rock Monster is made up of 4 pieces and two metal screws. A top half, a bottom half, a poseable arm, and a special internal component to hold the arm in place. The fascinating part of this story is that each internal component is a different random color that can exhibit different marbling patterns due to the way these parts were produced.
Where Does the Random Color Come From?
According to BrickLink.com, “The special internal part is currently the only known part to have been made in LEGO color 130 Colour Mix. This seems to have been a placeholder color to represent a blend of miscellaneous other colors. Thus, this special internal part exists in a wide range of varying colors.”
When other LEGO® parts are produced that don’t meet the company’s strict quality standards, such as short shots (When there isn’t enough plastic to fill the mold), mismolds, color issues, or other factory defects, they recycle the plastic in a process called regrind, where they grind the defective parts back up into plastic pellets. The catch with this process is that when you grind up a bunch of different colors of plastic together, you get randomized unofficial LEGO® colors. Since the internal component of the Rock Monster was never intended to be seen, this was a great way for the company to save money on plastic by using this industrial byproduct for a new purpose!
A History of LEGO® Marbled Pieces.
While there have been many common marbled pieces in sets from themes like Bionicle, Castle, Elves and more, they are all blends of two known colors, and have relatively uniform marbling patterns. One of the rarest and most expensive standard marbled parts was a Glow in the Dark Octopus from the Agents theme in 2008! There are also rare factory defect parts that exhibit marbled patterns from when they hadn’t fully flushed the lines of the injection molding machine after switching what color plastic was being used.
Back in the 1960’s and 70’s, an ABS plant in Grangemouth, UK was given a LEGO® 2x4 mold to maintain quality control in the supply chain. While many of these bricks were made in solid (albeit non-standard) colors, many were also made in marbled plastic also using regrind. You can read all about the history of Grangemouth LEGO® Bricks here and purchase them here!
We also have a number of marbled test trees in the old HO scale tree mold from the 1960's which you can find here.
How To Check Your Very Own Rock Monster
The Rock Monsters can be opened fairly easily without damaging them, but here are some tips for best results. NOTE: If you are a kid, make sure to ask an adult for help and don’t try this on your own! You will need: A small Phillips head (+) Screwdriver. On the underside of your Rock Monster, there will be two small, black Phillips head screws. You will want to carefully remove these, so as not to strip the head of the screw or the threads inside the plastic. We encountered at least one where the screws could not be removed, either due to rust, corrosion, or the plastic fusing. Don’t force it!
Make sure you don’t lose the screws. You should now be able to separate the top and bottom halves of the mold and reveal your own unique internal component! When reassembling, make sure you align the arm properly inside the socket so that it can swivel up and down without being able to be pulled straight out.
See All the Colors We Have at Atlanta Brick Co®!
We recently did a livestream where we opened up over 30 of these vintage Rock Monsters live on YouTube, which you can watch here!
If you’d like to order a Rock Monster with a specific color internal component, you can purchase one here and add in your order notes the corresponding number we mentioned on the livestream!
