A/N I do not know how long it took Fëanor to create the Silmarils, but I am assuming it took years to do considering how beautiful and powerful they were. It is said he put some of his essence into the jewels and they were also created out of a crystalline substance called silima which only Fëanor himself knows of.
# 20 Gems and Jewels
Fëanor stood back smiling as he admired his finished work. For years he had long labored in secret wanting to create the perfect jewels which reflected the Light of the Two Trees. He had poured his blood, sweat, tears, and even a part of his essence into these gems, and now they were finished.
Taking the three jewels in his hands, Fëanor carried them to the Valar. As he showed them his handiwork, they had gasped in astonishment as they had never seen anything so beautiful before.
"What are these jewels called, Fëanor?" Lord Manwë asked still admiring the gems which rested in Fëanor's hands.
Fëanor looked down at his work and thought for a moment. What was he going to call them? Finally, after thinking for a moment, he answered. "I will call them the Silmarils."
"Radiance of pure light," Lady Varda replied quietly. "Yes, that is a perfect name. Might I see them for a moment?"
Holding the Silmarils close, Fëanor was not sure he wanted to part with them quite yet. "What for, my lady?"
Varda laughed softly. "Worry not Fëanor; I will give them back. I only want to hallow them so no evil creature or mortal can touch them without justly deserving them."
Fëanor still was not sure, but after thinking about it, he hesitantly handed them over to Varda who blessed them. Afterward, she gave them back. "These jewels are a rare beauty, Fëanor. You have put much love into creating these, however, as with all jewels be careful not to let them consume you."
Taking the Silmarils, Fëanor covered them back up and bowed. Leaving, he did not yet realize the horrible fate to await him and of his kin all because three little Silmarils.