useless trivia: What Word Means: Something That Portends?

Questions

A wind with a speed of ---------- miles or more is designated a hurricane.?

About ---------- cars are junked each year in the U.S.?

According to the Gemological Institute of America, up until 1896, India was the only source for ---------- to the world.?

All snow crystals are---------- .?

All the gold produced in the past ---------- years, if melted, could be compressed into a 50-foot cube.?