Terry Herbert found a stash of 3,500 gold, silver and garnet-encrusted Anglo-Saxon-era artifacts with his metal detector.

It was an ordinary summer day in 2009 when a man with a metal detector hit upon a 1,300-year-old secret. Buried near the surface of a field in Staffordshire, England, was a stash of 3,500 intricately decorated pieces of gold, silver and garnet — the largest collection of artifacts ever found from Anglo-Saxon times, the era of “Beowulf” and the Book of Kells. The treasure hunter was unemployed 55-year-old Terry Herbert.

“I just couldn’t stop the items from coming out of the ground,” he later told National Geographic about the five days he spent digging.

Herbert received half the treasure’s assessed value of more than $5 million. (The money was raised by two museums in England that purchased the collection; the rest of the cash went to the farmer on whose land the items were discovered.)

But the hoard’s story hardly ends there. Scholars are just beginning to study the stash, which contained articles of war — including more than 300 sword-hilt fittings — and a few religious objects. Many pieces were damaged or broken, raising the questions of who buried the objects and why.

Experts believe this jeweled object adorned an Anglo-Saxon sword.

“For years to come, we’re going to be learning more about the hoard,” says Susan Norton, director of the National Geographic Museum, which borrowed about 100 objects for its “Anglo-Saxon Hoard” exhibit, on view through March 4.

Many of the artifacts are carved with miniscule patterns. Their detail makes conservators wonder how “some of the most intricate carving that anyone’s ever seen” was made without magnifying glasses — which probably weren’t invented until centuries later, Norton says.

The purposes of individual items also remain mysteries. Initial analyses are revealing clues about the objects’ origins, however.

Some of the gold was traced to the ancient Greek civilization of Byzantium, while the garnet may have originated in Bohemia, Portugal or India. “We refer to the period as the Dark Ages” and assume people weren’t very mobile during that era, Norton says. “But knowing now that the gold and garnet came from other places, what does that tell us about their trading routes? This is just a really compelling period of history that people haven’t known a lot about.”

National Geographic Museum, 1145 17th St. NW; through March 4, $8; 202-857-7588. (Farragut North)