In the mezzanine gallery of the Natural History Museum in London are some of its cherished treasures: the 1,384-carat Devonshire Emerald; a replica of Queen Victoria’s Koh-i-noor diamond; and the Aurora Pyramid of Hope, a rare collection of 295 naturally colored diamonds.


The emerald was once the property of a 19th-century Brazilian emperor, and the original Koh-i-noor, under guard in the Tower of London, is one of the crown jewels. The Aurora collection has somewhat humbler roots.


It was put together in the 1980s and ’90s by two men, Harry Rodman, a veteran gold refiner from the Bronx, and Alan Bronstein, a diamond dealer from New Jersey. Together they assembled the world’s most comprehensive grouping of colored diamonds and exhibited them at prestigious museums like the Smithsonian Institution in Washington and the American Museum of Natural History in New York.


But these days the fate of that collection and other gems is being decided on the fourth floor of Surrogate’s Court in the Bronx, a few blocks from Yankee Stadium.


Mr. Rodman died in 2008 at 99, and now his family is battling Mr. Bronstein over who is rightfully entitled to Mr. Rodman’s half-share of their collections, valued by one appraisal at more than $14 million.


The question is complicated by the fact that Mr. Rodman made seven wills in the last decade of his life and by the intermingling of family and business ties.


In addition to being Mr. Bronstein’s partner, Mr. Rodman in 2001, at 92, married Mr. Bronstein’s 81-year-old mother, Jeanette, his longtime friend and neighbor.


“Harry became my best friend, my mentor and my stepfather,” Mr. Bronstein said in an interview before a court hearing this week.


Mr. Rodman came from a family of jewelers. His father was a craftsman who supposedly made jewels for the czar in his native Russia, his nephew Gerald Gould said. He immigrated to the United States in 1903, crowding into a Lower East Side tenement to escape the pogroms that were terrorizing Jews in his hometown near Kiev. Mr. Rodman followed his father into the business, but made his name and his money in gold, Mr. Gould said, becoming a well-known figure in the diamond district in Midtown Manhattan.


“Walking down 47th Street with Harry Rodman was like walking down the street with the mayor,” Mr. Gould said. “Everybody knew him.”


In 1986, after 50 years in business, Mr. Rodman retired and sold his gold refining firm. By that point, he had already met Alan Bronstein, a young, ambitious dealer, whose mother, Jeanette, was a bookkeeper at the Diamond Dealers Club. Now considered one of the foremost experts on colored diamonds, Mr. Bronstein had what he once described in an article as a “burning passion” for the stones that was first piqued in 1979, when he saw “a fabulous canary yellow diamond that glowed with the hue of the sun.”


Colored diamonds were not particularly popular at the time, and little was known about them. Mr. Bronstein set about changing that.


“Colored diamonds are as varied as the faces of people,” Mr. Bronstein said at the courthouse.


About one in 10,000 diamonds is colored. Other elements in addition to carbon or a hiccup in the structure of the crystal is what gives a stone its particular hue. Colored and colorless diamonds are often found in the same mine.


Mr. Bronstein’s enthusiasm soon rubbed off on Mr. Rodman, and “collecting became our obsession,” Mr. Bronstein recounted in an article printed in a trade publication. Mr. Rodman put up the money and Mr. Bronstein did the research.


“Most of our time was spent running from place to place, trying to be the first to see a new stone that may have come off the cutting wheel, been imported from another country, or just been removed from an antique piece,” Mr. Bronstein wrote. They founded Aurora Gems, and split the business down the middle. The name came from Mr. Rodman, who frequently traveled with his first wife, Adele, and found that the varieties of color reminded him of the aurora borealis.