The Mirror-White Jewel is perfectly circular—down to the atom—and has no mass. It is not clear to you how. What is clear is that it can be tacked as if it were the knob to a door in timespace by making a standard REA check and burning X GRT, where X is up to the GM’s mood at the moment. (A good rule of thumb is the current average party level × 4 GRT.) Using the Jewel in this way comes with a 1 in 4 chance of triggering an Escheresque physics event. See “Folds” for more on Escheresque events.