The 39 Clues Wiki
The 39 Clues Wiki

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In order to unlock this clue, you must add the Desert Mystery Card Combo.


The Calcium Symbol


The Calcium Carbonate was hidden in Area 51,Nevada. A secret Lucian stronghold. Whenever the locals try to discover what was in there, the Lucians seize them and make it look like it was an alien abduction. The other branches use technology and devices to discover it, but they never succeed. Eisenhower Holt suspected there was a clue in Area 51, and he may or may not have stolen it from their Lucian rivals.


The screen shows the entrance of Area 51. Once we entered, an alarm goes off, making noises. Passed over the Lucian crest door, then the next door, and we arrived at cross-path. The screen goes to the left and we passed three doors, revealing a cube of calcium carbonate with lasers. Backed away, and the screen goes black with a word 'CALCIUM CARBONATE'


The Clue Calcium is unlockable by completing the Desert Mystery combo:

About Calcium Carbonate[]

Calcium Carbonate is also called CaCO3. It


The 39 Clues Clue 26

neutralizes hydrochloric acid (HCl).

Calcium Carbonate

Calcium Powder