these are the combos i tried:
diamond x stone (3 different stones)
diamond x turquoise (3 different turquoises)
diamond x mossrock (5 different mossrocks)
diamond x golem (3 different golems)
angel x stone (3 different angels & 2 different stones)
angel x turquoise
quetzal x mossrock (2 different mossrocks)
quetzal x turquoise
but yesterday i started to use epic diamond (vitrim) and a freshly new bred stone (level 7 COBBLE) again and it worked on 6th or 7th try!