Two years ago Nasdaq and Citigroup announced a new blockchain system they said would make payments of private securities transactions more efficient. Nasdaq Chief Executive Adena Friedman called it “a milestone in the global financial sector.” But the companies did not move forward with the project, Reuters reported Tuesday, because while it worked in testing, the cost to fully adopt it outweighed the benefits. From a report: Blockchain, the person added, “is a shiny mirage” and its wide-scale adoption may still “take a while.” In a joint statement, the companies said the pilot was successful and they were “happy to partner” on other initiatives. Both companies are also working on other projects. Companies, including banks, large retailers and technology vendors, are investing billions of dollars to find uses for blockchain, a digital ledger used by cryptocurrencies like bitcoin. Just last month, Facebook revealed plans for a virtual currency and a blockchain-based payment system. But a review of 33 projects involving large companies announced over the past four years and interviews with more than a dozen executives involved with them show the technology has yet to deliver on its promise.