The Happy Hollisters and the Castle Rock Mystery

The Happy Hollisters and the Castle Rock Mystery (#23 in the Happy Hollisters series)
An abandoned rock quarry, mysterious flying objects, and a valuable deposit of titanium lead the five Hollister children—Pete, Pam, Ricky, Holly, and Sue—into their latest thrilling adventure.
When a package of instruments from a weather balloon is parachuted onto their front lawn, the Hollisters are baffled and very excited. Just what is the meaning of the orange parachute and its dangling white box? The Hollisters connect the balloon with the strange lights which have been appearing at night over their Shoreham home, and once again they start off on a trail of detection.
A chance visit to a local “rock hound,” a man who collects minerals, proves to be the clue to the puzzle. Then their detective work takes them to a fantastic, spooky rock quarry which turns out to be the location of a hidden laboratory for weather experiments and also the scene of an attempt to steal some valuable titanium.