Fast of the Firstborn (Hebrew: תענית בכורות, Ta'anit B'khorot or תענית בכורים, Ta'anit B'khorim); is a unique fast day in Judaism which usually falls on the day before Passover (fourteenth day of Nisan). Feast of Unleaven Bread always begins on the fifteenth of the Hebrew month. Unlike most Jewish fast days, only firstborns are required to fast on the Fast of the Firstborn. Usually, the fast is broken at a siyum celebration (typically made at the conclusion of the morning services), which, according to prevailing custom, creates an atmosphere of rejoicing that overrides the requirement to continue the fast.
Can anyone tell me more about this custom, where it came from and why?
Can anyone tell me more about this custom, where it came from and why?

The gems are there, they just need dug up and held up to the light to see their clearness, color, clarity, and size. 