Complex sentence: For a time it was believed that the desert sand had simply melted from the direct radiant thermal energy of the fireball and was not particularly dangerous, thus it was marketed as suitable for use in jewelry in 1945.
Split into simpler sentences: For a time it was believed that the desert sand had simply melted from the direct radiant thermal energy of the fireball and was not particularly dangerous. Thus it was marketed as suitable for use in jewelry in 1945.