Kohl-enhanced eyes of an ancient Egyptian
Egyptian kohl cosmetic tube
Egyptian kohl cosmetic tube
Here's a more "modern" example...
Keith Richards of the Rolling Stones in case you didn't recognize the mug.
It's an unfair world when you realize how many beautiful women
this ugly, but talented, bastard has slept with in his drug-addled life.
Speaking of good-old Keith, the word kohl, referring to the eyeliner, has a shared etymology with the word alcohol. It's a bit convoluted, but the word was originally applied to a fine powder produced by the sublimation of a mineral called stibnite (more about this below). Sublimation produces a vapor from the mineral which then deposits as a powder. This powder was thought to represent the "essence" or "spirit" of the mineral.
The Arabic phrase (الكحل al-kuḥl) for "the kohl" (al is a definitive article in Arabic translated simply as "the") became the word alcohol as it made its way to European alchemists and was used to refer to any fine powder produced by the sublimation of a substance. By the 16th century, the term came to be applied to fluids obtained by distillation including "alcohol of wine" or ethanol - eventually becoming the word alcohol we're familiar with today.
Kohl has been made from a variety of materials - one of which is the mineral stibnite. Stibnite (Sb2S3) is a mineral with the chemical composition of antimony sulfide (the element antimony is abbreviated Sb because the ancient Greeks called the mineral containing it stibi (στἰβι) meaning "mark" (because it was used to make kohl, of course). Stibnite often occurs, sometime spectacularly, as radiating clusters of dull gray metallic crystals. It forms in hydrothermal deposits (hot groundwater typically in volcanic areas) and the American Museum of Natural History has a 1,000 pound specimen on display. Here's one particularly pretty example:
Stibnite (Sb2S3) with barite (BaSO4)
The name antimony comes from the Greek ἀντί + μόνος (anti monos) meaning "not alone" since it was believed never to exist in pure form. Greek naturalist Pliny the Elder called it platyophthalmos (πλατυόφθαλμος) meaning "wide-eye" due to its cosmetic use (kohl again). Antimony sits below arsenic on the periodic table and shares many of its properties including its toxicity. As with many toxins, it was frequently used for medicines throughout the ages (toxic materials often have antibacterial properties).
Some have speculated that Mozart accidentally killed himself by dosing with antimony-based medications (here's an interesting blog post about antimony). Kohl, by the way, has also been made from galena, a lead sulfide mineral, but that's a post for another time.
Original uses of kohl may have been practical - the antibacterial properties of antimony may have protected from eye infections, the oils usually mixed with the powdered kohl moistened the skin in this dry arid climate, and black around the eyes afforded some protection from the fierce sunlight (the same reason football players smudge under their eyes).
I'll close with a more attractive use of kohl than the Keith Richards example above - the classic, exotic, and mysterious Arabian woman's eyes.
It's easy to see why the use of kohl has remained popular for thousands of years.