Florite crystals in Granite (ushually formed 1 to 2 miles underground! ) I get these in high silver/galena/gold deposits old mine tailings and in a 3000 ft deep mine shaft in Los cerillos... They will "Glow" under a florescent light (black light)..
On the off chance its Asbestos take a fork and try to "Peel" the white off if its Fluffy and looks like Cotton its asbestos.. if it does you should be carefull to wash you thoroghly and put it in a sealed box.. be safe know your mineral Disasters! lol i still think is florite.