Crossword Clue: Black gemstone
Here's the answer to the Black gemstone crossword clue, with an explanation and where it has appeared.
Definition & answer: ONYX
The answer to "Black gemstone" is ONYX. Onyx is a 4-letter word made up of 1 vowel and 3 consonants, beginning with O and ending with X. In a crossword grid it occupies a 4-square slot, and each of its letters also forms part of a word crossing it — so even if the clue stumps you, the crossing entries will usually hand you enough letters to fill it in.
Origin & meaning
Onyx is a banded variety of chalcedony, prized in its glossy black form for jewelry. The rare X ending makes O-N-Y-X a valuable constructor entry.
Common usage
Onyx turns up frequently in crosswords precisely because of that letter mix. Short, vowel-friendly words like ONYX are a constructor's best friend: they interlock cleanly with longer entries and help a grid come together without awkward letter clashes. When you see a 4-letter slot and already have a crossing letter or two, ONYX is often quick to confirm — especially once the O or X is in place.
Crossword trivia
Because it is only 4 letters long, ONYX appears far more often in daily mini and themed puzzles than longer, more obscure words. Regular solvers come to recognize it on sight, and it is exactly the kind of entry worth committing to memory: the more common short words you know cold, the faster your solve times become.
Stuck on this clue?
If "Black gemstone" has you stuck, don't force it — jump to the clues crossing this slot instead. Filling in even one or two intersecting letters usually makes ONYX obvious. That crossing-first approach is the single most useful habit for improving at crosswords, and it works on everything from the quick daily Mini to a full Sunday grid.
This clue in different puzzles
The clue "Black gemstone" is just one way to arrive at ONYX. Across different puzzles and editors you may see the same answer clued as "Banded agate variety". Recognizing that a single answer can wear many clues is one of the fastest ways to level up as a solver.
Example sentences
- "I had the crossing letters, so writing ONYX into the grid took no time at all."
- "Onyx is the kind of answer that clicks the moment you spot one letter."
- "Seeing 'Black gemstone' in the clue list, an experienced solver pencils in ONYX almost immediately."
- "Once the O was confirmed by the crossing word, ONYX was the only entry that fit."