It took six days in space – and more than 18 hours of exploration on the moon's surface – for NASA astronauts David Scott and James Irwin to collect the 170 pounds of lunar rocks they brought back to Earth as part of NASA's Apollo 15 mission in 1971.

Anyone in the Tucson area this summer is probably no more than a half-hour car ride from a quarter-pound chunk of that haul.

A moon rock is on display through mid-August at the University of Arizona Alfie Norville Gem & Mineral Museum, thanks to a six-month loan from NASA. It arrived at the museum in early February, as the museum geared up for a grand opening in its new space at the Pima County Historic Courthouse during the annual Tucson Gem, Mineral & Fossil Showcase.

Weighing 4 ounces and measuring about 3 inches long, the rock is the largest sample that NASA loans to museums from its collection at Johnson Space Center in Houston, said Elizabeth Gass, exhibit specialist at the Alfie Norville Gem & Mineral Museum.

The rock can be found in the museum's Mineral Evolution Gallery, the first gallery that guests enter as they leave the lobby.

"It's a privilege to have this rock here," Gass said. "Not every museum qualifies to have one because of the strict security protocols needed to keep the rock safe."

Mark Kelly, a U.S. senator from Arizona and retired astronaut, was instrumental in helping the museum get the rock, Gass said. During a visit to the museum before its grand opening, Kelly noticed the museum did not have a moon rock and mentioned it to museum staff.

Later, before the museum had even filed an application for a moon rock loan, a NASA official called to ask whether the museum was interested.

Kelly, apparently, had reached out to his colleagues at NASA and "had made a good enough case that they called us," Gass said with a chuckle. He also helped expedite the application process, she added.

NASA Deputy Administrator Pam Melroy, during a visit to the UArizona campus earlier this month, expressed gratitude to Kelly for his help in getting the rock to the museum.

"I think NASA can afford to give away a slice of that rock. Because we're going back to get more," Melroy said, referring to the upcoming Artemis missions, which aim to land the first woman and first person of color on the moon.

Apollo 15 was the first of NASA's Apollo "J" missions, which provided astronauts more time to explore the lunar surface than previous Apollo trips. Scott, the mission's commander, and Irwin, the pilot of the lunar module, made the trip to the moon's surface; Alfred Worden, the mission's third astronaut, piloted the command module and remained inside the module as it orbited the moon.

The lunar module touched down in the plains near Hadley Rille, a valley on the moon. The area looks like the foothills at the base of many mountain ranges on Earth, Gass said.

Scott and Irwin spent roughly three days exploring the area. The mission marked the first time humans drove a car on the moon, with the pair logging 17.5 miles in the rover.

The rock that now sits in the museum was collected at Station 8, a site roughly 410 feet from where the lunar module landed. Station 8 is also where the astronauts set up the Apollo Lunar Surface Experiments Package, or ALSEP, which NASA used until 1977 to collect data on the lunar surface.

The rock is a piece of mare basalt, a volcanic mineral found on the flat lowlands of the moon, said Gass, who is also a geologist. Those lowlands, she added, can be seen in images of the moon taken from Earth; they appear as darker, shaded areas, contrasted against the brighter areas, which are mountains. According to NASA, lunar basalts can be as old as 3.3 billion years – older than 98% of minerals found on Earth.

The rock is at least the second moon stone that can be found in Tucson. The Pima Air & Space Museum also has a rock, on permanent loan from NASA, on display.

The Alfie Norville Gem & Mineral Museum stands out from other mineralogy museums as a destination to see both gems and minerals; minerals are inorganic solids that occur naturally in Earth's crust, while gems are minerals that have been combined with something else for aesthetics.

Although the moon rock is grounded in scientific discovery, there's plenty to admire about it for those who just want to look at something pretty, Gass said.

"Seeing an unaltered, unadulterated moon rock is really special," Gass said.

The Alfie Norville Gem & Mineral Museum is located at the Pima County Historic Courthouse, 115 N. Church Ave. The museum is open Wednesday through Saturday from 10 a.m. to 4 p.m., with the last tickets sold at 3. More information is available on the museum website.