volume of a hex in cubic feet?

[hal]

Hello Folks,
Has there ever been a definitive value given for the volume of a "hex" that is 6' in depth, and has the area of a single hex?

Page 31 of GURPS CLASSIC MAGIC has this to say about a hex where spells are concerned:

"In all these spells, one “hex” of earth, where it matters, is assumed to be six feet deep."

If a 1 yard hex has an area of 7.74 square feet, then a Hex in volume should be that times 6', or 46.44 cubic feet. There being 27 cubic feet per cubic yard, that is roughly 1.72 cubic yards per "Hex" of volume being affected in a GURPS CLASSIC MAGIC earth spell.



GURPS MAGIC changed some of the spell descriptions to do away with "hex" with respect to earth spells, and changed it to cubic yards.

I was curious how the two compared side by side.

GURPS CLASSIC MAGIC Shape Stone spell: Costs 4 energy per hex shaped, and 2 to maintain. That works out to roughly .42 cubic yards per energy point expended.

GURPS MAGIC for 4e: Costs 2 per cubic yard of stone, or .5 cubic yards per energy point expended.

GURPS MAGIC for 4e results in a slightly better or more efficient use of energy for the volume affected.



Thoughts? I got to thinking about this after reading Worminghall today and thinking "If the population density for the city is to take into account the unusable area of the city due to terrain issues (ie hills and cliffs), then how long would it take to remove some of those obstructionist bits of rock foundation for hills and hill tops, before the land becomes better suited for building? That in turn, led me to looking up formulas for areas of a hex, and volumes of a hex prism (right angle prism to be exact).