Ivory items put on display for reporters included scores of statuettes, a carved column, two pairs of tusks and a chess set.
Two pairs of tusks -- an adult elephant's and another from a young adult -- were valued at USD 200,000 and USD 150,000, respectively.
The ivory came from at least 12 slain animals, officials said.
"We are going to dry up... A market that only fuels the slaughter of elephants," Manhattan District Attorney Cy Vance said. "It is inexcusable, it is immoral."
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"This type of behavior will no longer be tolerated," he said.
New York was one of the first states in 2014 to adopt strict laws banning ivory sales to protect elephants, Vance said.
Undercover police posing as buyers seized the latest items at a midtown Manhattan art and antiquities store.
Although officials said they were not certain where the items came from, they did say most ivory craftsmen are found in China.
Although the store had a license, it expired two years ago and could not be renewed because of the new restrictions.
The store owners were indicted on charges of illegal commercialisation of wildlife. They face hefty fines and up to three years in prison.
The United States and China, among the world's biggest ivory consumers, have agreed to enact near-total bans on their domestic markets.
The Convention on International Trade in Endangered Species (CITES) banned the international commercial trade in African elephant ivory in 1989.
Savanna elephants have declined at a rate of 27,000 -- or eight percent -- per year, with a total of 144,000 lost in less than a decade.