How Diamond and Zircon differ in what they are, color, hardness and care.
| Diamond | Zircon | |
|---|---|---|
| What it is | The hardest known natural material, made of a single element, carbon. Only another diamond can scratch it. | A natural gem, not to be confused with man-made cubic zirconia. AGS calls it the oldest mineral on Earth: Australian zircons are about 4.4 billion years old. |
| Birthstone for | April | December |
| Colors | Colorless to light yellow or brown (graded D to Z); Fancy colors: yellow, brown, red, pink, orange, green, blue, purple, gray, black and white | Red; Orange; Yellow; Green; Blue (the December stone); Brown; Gold; Colorless |
| Mohs hardness | 10 | 6 to 7.5 |
| Toughness | Not stated | Fair to good, and can be brittle: facet edges can chip. |
| Everyday wear | Great for everyday rings | Wear with care |
| Ultrasonic cleaner | Use with caution; never for fracture filled diamonds; a jeweler should do it | Not recommended |
| Main sources | Formed deep below the Earth's crust and brought up in kimberlite, The first diamonds were mined along three rivers in India | Australia (about 37 percent of world supply), Thailand, Sri Lanka, Tanzania |
| Common treatments | A grading report says whether a diamond has been treated. Fracture filled diamonds should not go in an ultrasonic cleaner. | Commonly heat treated to make blue and colorless stones. |
Diamond is the harder of the two (10 on the Mohs scale). Choose by the color you love and how the piece will be worn; for a ring worn every day, the tougher stone will last better.
Sources: GIA: Secrets to keep your diamond sparkling, AGS: April birthstone, GIA: Zircon care and cleaning, AGS: Zircon. Checked October 16, 2026.
Birthstone of the month
On the first of each month: that month's birthstone, what it means and how to care for it.
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