Greetings Commanders 
Regarding the 'Large barnacles' - having made a quick check through this mountainous thread I couldn't see this mentioned, so just wanted to throw it out there. My apologies if this has been covered already, but here goes:
What are barnacles? Wikipedia gives us this description - "Barnacles are encrusters, attaching themselves permanently to a hard substrate". Ok, cool.
What are Meta Alloys? Part of the in game commodities mkt description gives us this - "Meta-alloys have a complex lattice structure with large internal voids. They are cellular in nature, and formed organically." Formed organically eh... hmmm.
We also get this - "These appear to be common in certain parts of space..." Certain parts of space eh... hmmm.
Now we know FD created an amazingly complex (and as scientifically accurate as possible) stellar forge that is responsible for the seeding of systems, and now with the release of Horizons, planets to. These planets come in a whole host of sizes and shapes and, more interestingly, colours. The planets get their colour from the elements injected into them via the stellar forge. This can be seen in the image below showing different coloured mineral deposits at the surface.
So my hunch is that these 'Large Barnacles' are called barnacles for a reason and that the "certain parts of space" possibly corresponds to planets with a particular geological makeup and/or with certain physical attributes. If correct, we will find these barnacles 'growing' on the right planets, in the right places. Farmers will tell you that in order to grow something, you need the right conditions. We just need to figure out what those conditions are.
Anyway - just a thought
Regarding the 'Large barnacles' - having made a quick check through this mountainous thread I couldn't see this mentioned, so just wanted to throw it out there. My apologies if this has been covered already, but here goes:
What are barnacles? Wikipedia gives us this description - "Barnacles are encrusters, attaching themselves permanently to a hard substrate". Ok, cool.
What are Meta Alloys? Part of the in game commodities mkt description gives us this - "Meta-alloys have a complex lattice structure with large internal voids. They are cellular in nature, and formed organically." Formed organically eh... hmmm.
We also get this - "These appear to be common in certain parts of space..." Certain parts of space eh... hmmm.
Now we know FD created an amazingly complex (and as scientifically accurate as possible) stellar forge that is responsible for the seeding of systems, and now with the release of Horizons, planets to. These planets come in a whole host of sizes and shapes and, more interestingly, colours. The planets get their colour from the elements injected into them via the stellar forge. This can be seen in the image below showing different coloured mineral deposits at the surface.

Anyway - just a thought