Technical term for this material structure?

[Nik_2213]

A massive rocky material that is connected open-cell, macro-porous at surface, but 'vesicles' shrink to closed-cell then solid as you drill deeper: What's the technical term for such ??
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Writing a SciFi tale, I'm trying to describe a large, alien-ish rock formation. I've a vague recollection of seeing a picture / drawing of similar terrestrial material, albeit more localised, but correct technical terminology eludes me...

The deep cliff-face material resembles monolithic black basalt, but surface is open-cell, macro-porous unto several cm diameter. The 'bubbles' shrink with depth, passing through 'sparsely connected' to smaller and smaller closed-cell vesicles, then none, diamond-cores revealing a solid mass beyond several metres.

Neither pumice nor Aaaa, their vesicles are too small, and don't seem to close at depth...

You could probably recreate the necessary topology with 3D printing...

Sorry, I began to post this query in 'Earth Sciences', then realized mentioning 'SciFi' & 'alien-ish' meant it probably belonged here.
;-)

 

[BillTre]

Sounds like it could be a liquid rock containing lots of bubbles due to over-saturation with gasses.
The bubbles can sort vertically before the rock solidifies, due to differences in their rate of rising in the fluid rock (larger rise faster).
I have seen rocks in Hawaii with gradients of bubbles like this, but I don't recall any that were open cell.
On the other hand, the rocks of the island (the Big Island, where fresh rocks are being made) are porous (or at least pervious), in places. Ponds (brackish) in peoples yards would go up and down with the tides.
The open cell state would require a lot of gas, or prolonged sorting of the bubbles from a large, lower region of (in the end) bubble free fluid rock, prior to solidification.

 

[Klystron]

For choosing a name for your alien rock structure this list of rock types may be useful. I like the term igneous rock. It looks and sounds good describing fiery origins and may even be correct.

 

[chemisttree]

I would call it “graded intumescent”.

 

[Nik_2213]

Thank you !

 

[256bits]

Maybe a tuff rock formation could be used, where the bottom layers become compacted.
https://en.wikipedia.org/wiki/Tuff

 

[stefan r]

An aerogel is a type of thing. Foam has more solid.