Economic transactions are recorded from registered businesses only. That is, informal trades are not recorded. In your example, trading a stone wouldn't be a registered business activity. However, let's assume it is.
GDP is the final value of goods and services produced, so as dismalscience says, intermediate goods are not recorded. Let company A sell a stone to company B. The stone that company B holds would be seen as an intermediate good, as the product that company B sells uses that stone as an input. In this example, the intermediate good is coincidentally also the final good (no value is added). The value of the stone will only be counted once.
That being said, stones don't get sold for \$1 million. Even if two parties signed a contract that forces the second party to sell the stone back to the first party, they would both be in the same situation after the two transactions—the first party would have the stone, and the second party would have their \$1 million. (There is a disincentive to do this because the government will tax it.) The same logic can be extended to a collection of parties who pass on the stone to each other in a circle. In the end, they all are back at square one. It is plausible that (given the difficulty with which one secures \$1 million credit) people aren't motivated to skew GDP figures by engaging in this type of activity, also given the costs involved with the activity such as tax.