Is there something more special about ZEN in comparison to NGC's deposit?

Absolutely. Hydrothermal (vein) graphite is very different than metamorphic (flake) graphite.

ZEN's graphite has extremely small particle sizes. Viewing core under my 16X loupe, I was unable to detect individual crystals. Because of the small particle size, all the graphite molecules are randomly oriented. Therefore any sample of this graphite will have uniform electrical properties in three dimensions. It will be isotropic.

In contrast, flake graphite is arranged in stacked sheets. The electrical properties are anisotropic, as they are oriented in the plane of the sheet.

In order to get to a product that is useful in battery electrodes, for example, the flake graphite has to be converted to spherical graphite, so that it can obtain some randomness in particle orientation, and show some isotropic character. But that is very expensive.

First, the purity of the flake has to be obtained. That is done by multiple stages of flotation, each stage of which has less than complete yield. To get flake to 99% Cg, you're probably talking 30% yield, or less. Then, you have to mill the flakes, to break them into small enough pieces such that their 3-dimensional dimensions are roughly equal. Basically, they're intentionally destroying the flake character. Again, yield will suffer some losses. And this is all to approximate the inherent characteristics of both synthetic and hydrothermal graphites, which are both small-particle spherical graphites.

All ZEN has to do to produce electrode-grade graphite is a single step process, with no loss in yield. They dissolve away the feldspar and silica, and they're done.

In your terms, ZEN is "more special" then e.g. NGC.

Lar