It was and still is, the most expensive dye on earth.
 
Murex trunculus sea snails can only be collected by diving and hand-searching on rocky coastlines. A special gland inside the snail contains the valuable dyestuff which is removed and dried for further use.  This dyestuff is not just collected for the color, the glands are a by-product of the snails that are eaten as a fried snack in the Mediterranean.
 
Tyrian purple and tekhelet are two colors that can be produced with the murex trunculus, and for this you have to make a reduced vat, just like with indigo. If you are not doing anything special to your vat, it will give purple on wool and blue on silk.
 
The package of dye contains 10 grams which is enough for a two-liter hydrosulfite vat. It comes in a special box with instructions on producing Tyrian purple and blue, and includes the soda ash and sodium hydrusulfit needed.
 
Our special edition metal box comes with two pieces of French 18th century walked wool in a metal keepsake box.
 
I have written an extensive blog on the subject of tekhelet blue and tyrian purple that you can read here.