It's prudent to be wary of Wiki-quotes, but this much (above) is basically a paraphrase from part of Tolkien's [deep breath]...
"OF THE LAWS AND CUSTOMS AMONG THE ELDAR PERTAINING TO MARRIAGE AND OTHER MATTERS RELATED THERETO: TOGETHER WITH THE STATUTE OF FINWE AND MIRIEL AND THE DEBATE OF THE VALAR AT ITS MAKING"I'm not shouting... it's written like that in the book,
Morgoth's Ring
Somewhat stunningly perhaps (given my experience anyway), the above Wiki-description is rather good, if not as detailed as the text itself (not surprisingly), and I'll add the small detail that the slender rings of gold were worn upon the index finger of the right hand (the hand is not mentioned above, and the betrothal rings were silver), and that the custom of jewel giving begins with a new paragraph, starting with:
"Among the Noldor also it was a custom that the bride's mother..."But anyway... that's the source... I know you've been wondering for years
