Even among astronauts, Neil Armstrong gets special respect — he was, after all, the first man to walk on the moon.

On Tuesday, the Apollo 11 astronaut got a piece of the moon rock he brought back to Earth.

"I get to keep it myself only so long as I speak today. So I'm going to be talking longer than usual," Armstrong, 75, joked at a ceremony in which NASA presented him with the rock.

The rock — about 2 grams of medium light gray, fine-grained basalt encased in clear plastic — was part of NASA's Ambassadors of Exploration award. It was created to commemorate the 35th anniversary of the July 20, 1969, moon walk by Armstrong and fellow astronaut Buzz Aldrin.

NASA has also designated the astronauts of the Mercury, Gemini and Apollo programs as Ambassadors of Exploration.

Armstrong accepted the award at the Cincinnati Museum Center, where it will be on permanent display. About 200 guests attended.

Armstrong enjoys his privacy and has a reputation for not liking to talk about himself or his accomplishments, and he stayed true to form. He talked at length, however, about the formation of the universe and how the 3.7 billion-year-old moon rock related to changes that occurred on Earth.

John Glenn, who has orbited Earth and has been a U.S. senator from Ohio, said he's usually not envious of others, but for Armstrong, "I make a big exception."

"I envy Neil for that wonderful, wonderful experience," he added.