What Makes a Black Stud Earring Black?
Summary
A black stud can be black diamond, onyx, spinel, enamel, glass, ceramic, or metal with a black coating, and the post behind it may be a different material again. A thumbnail rarely shows which.
With diamonds, the question is treatment. GIA’s page on diamond treatments is blunt about it: “In fact, most black diamonds are treated.”
Four details decide what you are getting: the black material, the face-up size in millimeters, the metal of the setting and post, and the type of back.
Two pairs can look the same and be made of different things
Two 5 mm black studs can be indistinguishable in a thumbnail and still be completely different products. One may be onyx in sterling silver. Another may use treated black diamonds in 14K gold. A third may be stainless steel with a black finish and no gemstone at all.
Ask how a black diamond got its color
GIA’s fancy color diamond buyer’s guide says: “The opaque color of black diamonds is caused by dark inclusions or, more commonly, by color treatment.” GIA’s treatment page describes annealing, a controlled heating and cooling of the stone, as very common for creating black diamonds.
A treated black diamond is still diamond, and GIA grades annealed stones because the treatment is stable. Its treatment page also states that “Wholesalers and retailers are required to disclose the presence of treatments.” Coating is a different matter. GIA describes it as a thin layer of foreign material over the stone, says “Coatings will scratch and wear off over time and can be damaged by heat and/or chemicals,” and does not issue reports for coated diamonds.
Natural-color, treated, and laboratory-grown black diamonds are three different products. If the listing stops at “black diamond,” you have not been told which one it is.
Onyx, spinel, enamel, and coated metal create different kinds of black
Onyx gives a smooth, opaque surface. Faceted black spinel returns more light and looks sharper. Enamel gives a flat, graphic finish, and a black coating on metal can produce a clean minimal look with no gemstone at all.
GIA lists onyx as a form of chalcedony and notes on its August birthstone page that sardonyx, “like other forms of chalcedony, is commonly dyed.” Our article on black pendant stones compares the hardness of onyx, spinel, and black diamond. For studs, the finish is what you see: a flat black dot comes from a smooth opaque stone, and flashes of light come from facets. A video or several photos of the actual surface show which one you are looking at.
The post is its own question
The part that goes through the ear decides comfort and metal sensitivity. A black stone in a precious-metal setting does not mean the post or back is made of the same metal.
A listing that names the stone and says nothing about the post has answered half the question. The metals to look for are listed in our sensitive-ears article.
With a coated black-metal stud, the finish hides what is underneath, and the metal underneath is what touches the ear.
A few millimeters make a large visual difference
Black creates strong contrast against skin and hair, so size changes the effect quickly. A small stud can read almost like punctuation; a larger disc or gemstone becomes a graphic feature.
Measure the front of a stud you already wear and check it against the listing. A 3 mm stud and a 5 mm stud are only 2 mm apart across the face, yet the 5 mm stone covers almost three times the area.
Looking for a piece? Browse earrings in the feed →
Sources
We have not tested any products. Details are as published on these pages on the date above and can change; the seller's or maker's page has the current version.