Septarian nodules mystery: minerals formed in partitions?

Septarian nodules (Septarian concretions) are amazing looking marbles, rocks and up to the size of boulders that have crazy patterns. Perhaps the most famous examples are the Moeraki Boulders in New Zealand.

A number of Septarian nodules can be found on the Norfolk/Suffolk border. The one photographed here (about 20 cms wide) has the strange pattern but also has minerals that appear to have been formed in the partition pockets.

Minerals in partition mystery

One surprise is that the minerals appear to stop at the boundaries of the septaria (crack or cavities), looking like they have formed in that partition only.

There is one part on this particular nodule where slightly different mineral is formed either side of a septaria. Has the crack gone through the same material or has it formed a variation of the same mineral?

Minerals and crystals are often found in vugs (pockets) in the host rock. They also can be formed along viens, these often resemble Lichtenberg patterns or lightning discharge patterns.

Septarian nodules formation mystery

No one knows how Septarian nodules and Septarian concretions are formed and why they are that shape and pattern.

Minerals are meant to be formed deep in the ground under high pressure and high heat. But why are precious stones found on the surface or very close to it?

Could they be formed where they are found? Could powerful electromagnetic forces produce the high energy, heat, pressure needed to transmute the host material into other minerals? As well as the pattern.