Riddonkulous

I’m light as a feather, yet born to begin,
 a delicate thing that lets warmth enter in. I’m gathered for when the weather turns cold, taken from nature, quiet and old. I need only a spark, a flicker, a glow,
 and suddenly light begins to grow. I can be kindling, yet mostly not quite,
 a glimmer of hope in the dark of night. 
 What am I?