These lines come from a poem writen by the American poet Linda Pastan The name of this poem is “Egg,” and in here she mentions the physical characteristics of that egg. She uses the symbolism to give the egg a dynamic power.
"the first delicate crack of lightning" is an example of the dynamism and power given to the egg through the expression lightning. The symbolism is atechnique that uses symbols to give qualities to objects, like an egg using sometinmes other object, like a lightning.
Symbolism can take different forms. Generally, it is an object representing another, to give an entirely different meaning that is much deeper and more significant.
