In an attempt to find out if the crystal was pure crystalline quartz and not glass or another mineral, Hewlett-Packard submerged the crystal in Benzyl alcohol, which has almost the same refraction index as quartz. The skull became invisible inside the tank, showing that it was indeed pure crystalline quartz.
Marion and Jones walk into the [insert bad guy's name]'s library, sunbeams filtering through large windows framed by heavy drapes. Jones' eyes roam over the immense room, taking in the wall-to-ceiling shelves full of books lining the walls. Expensive oriental rugs cover the floor, and overstuffed leather chairs and tables are arranged across the great expanse. A suit of shined armor stands next to one window with a set of swords displayed on the other side. A large painting covers part of a wall absent of bookcases, with a large overstuffed leather couch spread underneath it. A small fish tank sits on a table to one side. On the other side a table holds a bust of --
Jones eyes dart back to the fishtank. The corner of his mouth lifts in a grin. He strides over to the tank and pulls off the top and plunges his hand into the tank, splashing water over the sides as he sweeps through the tank with his fingers spread wide.
Marion is freaked. Looking over her shoulder at the open door behind them, she rushes up behind Jones whispering furiously:
Marion: What are you doing?! Are you crazy?! Get out--
She stops short as Jones triumphantly pulls a crystal skull out of the water and holds it dripping in front of him.
Jones: Give me your bag.
Marion looks at him, mouth open.
Jones impatiently grabs the strap of her oversized bag off her shoulder and dumps all her stuff out on the floor as he shoves the skull into the bag. Marion stands aghast, watching Jones kick the contents of her purse under the couch. Then it sinks in: Jones has found the skull. She frantically joins Jones in shoving the remaining items under the couch. She whispers in a low voice--
Marion: How did you know?
Jones: No fish.
Marion: No fish? But--
He grabs her hand and pulls her across the library, peeking around the door to see the hall is empty. He pulls her out of the library and down the hall to stairs. As he goes, he eplains in a low voice--
Jones: There weren't any fish because fish can't live in benzyl alcohol, which has almost the same refraction index as quartz.
They are at the bottom of the stairs now and Jones pulls her across the wide foyer towards the front door. He glances at Marion, who's still confused. He whispers--
Jones: It makes the skull look like its invisible.
A voice coming from a room across the foyer stops them in their tracks--
Bad guy: Leaving so soon?