Possibly a joining of astragalomancy and gyromancy (spinning of the dice). <span class="searchmatch">astragyromancy</span> (uncountable) Divination by dice. 1970, Richard Cavendish, Man, Myth...
Souvenir Press, published 1987, →ISBN, page 312: ASTRAGALOMANCY or <span class="searchmatch">ASTRAGYROMANCY</span>: Divination with dice, ranging from crude bones with primitive markings...
apantomancy arachnomancy archaeomancy arithmancy armomancy astragalomancy <span class="searchmatch">astragyromancy</span> astromancy austromancy axinomancy barrelmancy belomancy bibliomancy...