Hexaplex trunculus degrades, resulting in blue only. Nonetheless, archeologists have confirmed Hexaplex trunculus as the species used to create the purple-blue dye; large numbers of shells were recovered from inside ancient live-storage chambers that were used for harvesting. Apparently, 10- to 12,000 murex yielded only one gram of dye. Because of this, the dye was highly prized. Also known as "Royal Purple", it was prohibitively expensive and was only used by the highest ranking aristocracy. A similar dye, "Tyrian purple", which is purple-red in color, was made from a related species of marine snail, "Murex brandaris". This dye (alternatively known as "imperial
Squaraine dye Squaraine dye Squaraine dyes are a class of organic dyes showing intense fluorescence, typically in the red and near infrared region (absorption maxima are found between 630 and 670 nm and their emission maxima are between 650–700 nm). They are characterized by their unique aromatic four membered ring system derived from squaric acid. Most squaraines are encumbered by nucleophilic attack of the central four membered ring, which is highly electron deficient. This encumbrance can be attenuated by the formation of a rotaxane around the dye to protect it from nucleophiles. They are currently used as sensors for ions and have