The unprecedented case is the first under the charge of aggravated crime against relics, which carries up to four years in prison, The Local reported.
An unauthorized dig of 250 pits was found in a field in Gandarve in October 2009, and last November police recovered an 11th-century hoard of 2,000 silver coins from Germany, England and the Arab world with an estimated value of 1.2 million kronor ($198,000).
A fragment of a crucifix found at the scene led police to the suspects when an e-mail from a Stockholm coin dealer offering a matching piece for sale was discovered.
Investigators raided the dealer's property on Gotland and found muddy clothes, metal detectors, shovels, backpacks and night-vision gear.
There were 18 reports of unauthorized digging on Gotland in 2009, but none since the suspects were arrested, authorities said.
Landowners who discover ancient artifacts get a finder's fee for turning them in to archaeological authorities.