Green’s Dictionary of Slang

snowflake n.²

cocaine.

1915		Bisbee Dly Rev. (AZ) 26 Aug. 6: These hopheads [...] will do anything [...] to get money to buy opium, morphine, ‘snow flakes’ and similar drugs.
1959		J.E. Schmidt Narcotics Lingo and Lore.
2005		Mad mag. Sept. 45: Johnny Snowflake?!? The Yayo?!? Booger Sugar?!?