Eventually, he went west, and with three partners,[a] formed a mining corporation and discovered the "Big Bonanza" in Virginia City, Nevada, which became the largest single deposit of gold and silver ever found.

More than $100 million worth of gold ($3.7 billion in today's currency) was extracted from that mine before it was exhausted in 1898, making all of them very wealthy.

He was eventually reconciled with his daughter Ellin and her husband Irving Berlin when he went to comfort her on the cot death of her baby.

[12] Because of religious convictions (he was a traditional Irish-American Catholic), Mackay would not remarry as long as his first wife, Katherine, lived.

Therefore, Clarence and Anna Case (1888–1984) waited until after Katherine's death in 1930, and were subsequently married in on July 18, 1931,[13] at St. Mary's Roman Catholic Church in Roslyn, New York.

Taken with her beauty, he sent a carload of flowers to her at her next Carnegie Hall recital, enclosing a small diamond band with an enamel bluebird in the center.

Clarence Mackay was a noted collector of medieval suits of armor, some of which he sold to the Metropolitan Museum of Art in the early 1930s.

An aviation trophy, administered by the United States National Aeronautic Association and awarded yearly by the United States Air Force for the "most meritorious flight of the year" by an Air Force person, persons, or organization, is named in Mackay's honor.