An ico-spectrogram, or icogram, was a geological test used to confirm the presence of dilithium ore in planetary crusts. It took approximately five hours to set up the equipment to perform an icogram.

In 2365, the crew of the USS Enterprise-D used an icogram to discover a very rare type of dilithium ore formation in the crust of Drema IV in the Selcundi Drema sector. (TNG: "Pen Pals")