Tom Swift Among The Diamond Makers; Or, The Secret Of Phantom Mountain

Volume 7 of the first Tom Swift novel series, written and published by Grosset & Dunlap, is titled Tom Swift Among the Diamond Makers, Or, The Secret of Phantom Mountain.
Diamonds are supposed to be a girl's best friend. Based on this conviction, Tom Swift is purchasing a diamond pin for Mary Nestor in a neighborhood jewelry shop. Mr. Jenks from Earthquake Island (a locale in the previous Tom Swift novel) visits the store and advises Tom not to buy a diamond there when the store owner abruptly departs the establishment to pursue someone who may be preparing a theft. Tom would receive a far better diamond from him that was created in Phantom Mountain. The next Tom Swift adventure starts at this point.
In the novel Tom Swift Among the Diamond Makers, Tom Swift sets off in the airship Red Cloud in quest of Phantom Mountain and the diamond makers there with Mr. Jenks, Mr. Damon, who is always around, and Mr. Parker, the "Debbie Downer" of scientists. Tom Swift would be up against some group of outlaws in the early Tom Swift novels. Mother Nature was the foe on Earthquake Island. Both are there this time, posing threats to the protagonist and his companions.