Star Sapphire rough

Hello I posted a similar question before, Yet I am trying to learn how to identify a piece of rough that may produce asterism. I have some material of rough ruby and sapphire, it was a bulk Amazon cheep buy I was just hoping it would contain some material however small that was facet grade. It does not but there are a few pieces that may make a decent Color cab. Is there a way to look at a piece of rough to determine if it may yield a star sapphire? This material has a strong laminar cleavage I found after tumbling.
To bring out asterism how should I orientate the stone in relation to the cleavage? And is it a hit and miss excersise.

Thank you Kindly

Hi if the sapphire may star it should show a reasonable sheen on the top and bottom of the crystal axis (looking directly down the crystal). you would cab the sapphire as per this orientation. top and base would be top and bottom of crystal directly down the axis
good luck

Thank you that give me an appreciated place to start.