Last Updated: April 2026
TL;DR:
- No — CZ is graded A through AAAAA (sometimes marketed as “6A”), and the difference between a bottom-tier A stone and a top-tier AAAAA stone is night and day in cut precision, clarity, and sparkle.
- Grade depends on 3 things: facet cut accuracy, clarity (inclusions), and polish — not just the letter on the listing, since the A-grade system has zero third-party oversight.
- AAAAA-grade CZ scores 8.5 on the Mohs hardness scale and runs a refractive index near 2.15-2.18, close enough to a diamond’s 2.42 that most people can’t tell the difference across a room.
I’ve cut and set thousands of cubic zirconia stones on the factory floor, and the question I get more than any other is whether all CZ is basically the same. It isn’t. Cubic zirconia quality swings wildly depending on the grade, the cutter, and where the rough material came from. This guide breaks down exactly how CZ grading works, what separates a $3 stone from a $30 stone, and how to spot the difference before you buy.
Are All Cubic Zirconia Stones the Same Quality?
No. Cubic zirconia stones are graded on a 5- or 6-tier scale — A, AA, AAA, AAAA, AAAAA, and sometimes a top “6A” or Diamond CZ tier. The lowest grade has visible flaws and a dull cut; the highest grade is nearly flawless with diamond-grade faceting. Price, clarity, and sparkle all shift with the grade.
Here’s the catch: unlike diamonds, cubic zirconia has no independent lab — no GIA, no AGS — certifying these grades. International Gem Society notes that CZ grading is a manufacturer-driven marketing system, not a scientific standard. That means a “AAA” stone from one factory can look better than a “AAAA” stone from another. I’ve seen it happen on my own production line — two suppliers, same grade label, completely different light performance.
What doesn’t change is the chemistry. Every CZ stone is synthetic zirconium oxide (ZrO2), grown in a lab because natural zirconia deposits are too rare and too small to mine commercially.
The A-Grade System: What Each Tier Actually Means
Jewelers rank CZ from lowest to highest like this: A, AA, AAA, AAAA, AAAAA (5A), and Diamond CZ 6A at the very top. AAA is the workhorse grade — it’s what most costume and fashion jewelry uses because it balances sparkle against cost. If you want to go deeper on the tier system, I wrote a full breakdown in our 5 common CZ grades guide.
| Grade | Mohs Hardness | Clarity | Typical Use |
|---|---|---|---|
| 6A / Diamond CZ | 8.5 | Flawless, precision-cut | Fine jewelry, gold/platinum settings |
| AAAAA (5A) | 8.5 | Near-flawless | Premium fashion jewelry |
| AAAA | ~8.5 | VVS-equivalent, minor inclusions | Mid-to-high fashion jewelry |
| AAA | ~8.5 | Some visible inclusions | Most costume jewelry |
| AA / A | 8 | Frequent inclusions, dull cut | Bottom-tier, disposable pieces |
What Is the Highest Grade of Cubic Zirconia?
The highest grade is Diamond CZ 6A, followed closely by AAAAA (5A). Both are cut to near-diamond proportions, flawless to the naked eye, and set almost exclusively in real gold, platinum, or sterling silver rather than base metal.
For a deeper look at exactly what pushes a stone into that top tier, I broke it down piece by piece in what is 6A cubic zirconia and what is 5A cubic zirconia. Both grades run a refractive index between roughly 2.088 and 2.176 — a diamond sits at 2.42 — so the fire is slightly different, but under normal lighting most people can’t tell.
Facet Cut and Polish Separate Good CZ From Bad CZ
Grade letters get the attention, but the cutter’s skill is what actually makes a stone sparkle. CZ is cut in the same brilliant, princess, and emerald shapes as diamonds, and a precise 58-facet round brilliant cut returns far more light than a rushed, shallow cut with mismatched facet angles. On the factory floor, this is where cheap stones fall apart — the rough material might be fine, but a sloppy cutter wastes it.
Jewelry Secrets points out that low-grade CZ often comes from rough that’s too thin to hold a standard diamond-depth cut, forcing cutters to shortcut the pavilion. That’s why a cheap A-grade stone looks flat and glassy instead of fiery, even though the chemistry underneath is identical to a AAAAA stone.
Does a Diamond-Like Carbon Coating Make CZ Better?
Yes and no. A diamond-like carbon (DLC) coating, applied by chemical vapor deposition, adds a thin layer that mutes the stone’s rainbow “disco ball” flash and pushes its light return closer to a real diamond’s white sparkle. It does not improve the stone’s underlying clarity, cut, or hardness.
Coated stones are sometimes marketed as “diamond-coated CZ,” which oversells what’s happening — you’re getting a cosmetic finish, not a structural upgrade. GIA’s lab characterization of coated CZ confirms the coating sits on the surface and can wear off with enough handling, which is worth knowing before you pay a premium for it.
Swiss CZ vs. American-Cut CZ: Does Origin Matter?
Swiss-cut CZ has a reputation for tighter cutting tolerances — cleaner facet junctions, more consistent culet alignment, and more controlled light return through the crown. American and Asian-cut CZ can match that quality, but there’s no certifying body enforcing it either way. Because there’s no GIA or AGS equivalent for CZ, the “origin” label matters less than asking the seller directly what grade and cut standard they use, and requesting a close-up photo before you buy.
This is the same reason two stones with identical grade labels can look completely different once they’re mounted — the label describes an intention, not a guarantee.
How Can You Tell High-Grade CZ From Low-Grade CZ at Home?
Hold the stone under a single bright light and rotate it slowly. High-grade CZ throws sharp, distinct flashes of white and rainbow light with no cloudy zones. Low-grade CZ looks hazy, shows visible internal lines or bubbles, and the sparkle blurs together instead of flashing in distinct points.
You can also check the setting metal. Diamond CZ 6A and AAAAA stones are almost always set in real gold, platinum, or solid sterling silver because manufacturers don’t waste a premium stone on cheap base metal. If you want to know whether your CZ jewelry can hold up to daily wear, our guide on how long cubic zirconia lasts covers the durability side in detail.
CZ vs. Diamond: The Weight and Durability Difference
Even top-grade CZ isn’t a diamond, and the two behave differently once they’re in daily use. CZ weighs up to 1.7 times more than a diamond of the same dimensions, which is why jewelers size CZ by millimeter rather than carat. CZ also doesn’t conduct heat the way a diamond does — a trick some people still use (unreliably) to spot a fake. For a full side-by-side, see our breakdown of the main differences between cubic zirconia and diamond. If you’re deciding whether the stone is worth anything on resale, I covered that separately in is cubic zirconia worth any money.
The Bottom Line
Cubic zirconia is not one product — it’s a range, from A-grade stones that look glassy and flat to Diamond CZ 6A and AAAAA stones that fool most people at arm’s length. If you’re buying CZ jewelry, ask for the grade in writing, check whether it’s set in real gold or sterling silver (a sign the maker trusts the stone), and inspect it under a single light source before committing. Skip unlabeled “CZ” listings with no grade at all — that’s almost always A or AA quality dressed up with good photography. Browse our jewelry metals and materials guides for more buying research before your next purchase.
Frequently Asked Questions
What is the highest quality cubic zirconia?
Diamond CZ 6A is the top tier, followed by AAAAA (5A). Both are cut to near-diamond proportions, flawless to the eye, and typically set in real gold, platinum, or sterling silver rather than plated base metal.
What is the lowest quality cubic zirconia?
A-grade CZ is the lowest and cheapest tier. It has a Mohs hardness around 8, frequent visible inclusions, and a shallow cut that limits its sparkle compared to higher grades.
Can you tell cubic zirconia grades apart just by looking?
With practice, yes. Low grades look hazy with blurred, weak flashes of light. High grades throw sharp, distinct white and rainbow flashes with no cloudy zones. A jeweler’s loupe makes the difference obvious in seconds.
Does a higher CZ grade mean it lasts longer?
Not necessarily for hardness — most grades sit around 8-8.5 on the Mohs scale regardless of tier. Higher grades resist visible wear and dulling better because the cut and polish are more precise, so scratches and cloudiness show up more slowly.
Is AAA cubic zirconia good quality?
Yes, for the price. AAA is the industry-standard grade for most fashion and costume jewelry — optically flawless to the naked eye, heat-resistant, and far more affordable than AAAA or AAAAA stones.
Why doesn’t cubic zirconia have an official grading certificate like diamonds?
Because there’s no independent lab — no GIA or AGS equivalent — that certifies CZ. The A-grading system is set and applied by manufacturers themselves, so the same letter grade can mean different things depending on who cut the stone.
Tiger is a fashion&jewelry lover. He is also a fashion jewelry manufacturer that help thousands of small business to grow and also do business with some big fashion jewelry brands. He is a truly metal expert and he will share some information you are looking for.