What Is an Asscher Cut Diamond? The Complete Guide

The asscher belongs to the step-cut family, the same family as the emerald cut. A step cut is faceted with long, flat planes arranged in parallel rows, like the steps of a staircase running toward the center of the stone. There are no tiny triangular or kite-shaped facets scattering light into a fine sparkle. Instead the flat planes behave like mirrors, so an asscher returns light in broad, clean flashes rather than the small fiery pinpoints of a brilliant cut. If you want the wider distinction between the two faceting families, our diamond shapes guide lays every common outline side by side.

What makes the asscher its own shape is that those step facets are arranged around a square, not a rectangle. The corners are cropped, and the facets run concentrically inward from all four sides at once. Look straight down into a well-cut asscher and the crossing lines of the step facets and corner facets form an X that appears to spin toward the center. That is the "windmill," sometimes called the pinwheel, and it is the single most recognizable feature of the cut. The deeper and more symmetrical the steps, the more pronounced the windmill and the sense of looking down a tunnel of mirrors.

A standard asscher is cut with 58 facets, the same count as a round brilliant but arranged completely differently. Because the flashes are large and the pattern is geometric, the asscher reads as architectural and quiet rather than sparkly. It rewards clean lines and good symmetry, and it looks its best in strong, directional light where those broad planes have something to reflect.

Three structural traits give the asscher its depth and its durability, and they are worth stating plainly.

One practical consequence of that architecture: an asscher carries more of its weight in depth than a shallow, spread-out shape does, so a given carat weight faces up a little smaller than a comparable brilliant. You are paying for a deep, dimensional stone rather than maximum surface area. That is a property of the geometry, not a flaw, and it is part of why the cut looks the way it does.

The proportion that keeps an asscher an asscher is its length-to-width ratio. Take the length and width in millimeters from the grading report and divide the first by the second. An asscher should come out near 1.00, which is what makes it read as square. In practice, anything from about 1.00 to 1.05 still looks square to the eye. Once the ratio climbs past that, the stone starts to read as a rectangle, and a rectangular step cut is an emerald cut, not an asscher.

Because a report describes the measurable geometry rather than the trade name, this is also how you confirm what you are buying. A stone can be sold as an "asscher" while its measurements tell a different story, so read the numbers. For the full walkthrough of a certificate, see our guide to how to read a diamond grading report. Which exact ratio you prefer inside that square window is taste, not a grade, so look at the actual stone rather than chasing a decimal.

This is the single most important buying point for an asscher, so it is worth being direct about. A brilliant cut breaks light into hundreds of small flashes, and all that busy sparkle hides small inclusions and faint body color. A step cut does the opposite. The open table and long, clean facets act like windows into the stone, so anything inside has fewer places to hide. An inclusion that would vanish in a round brilliant can sit in plain view through the top of an asscher.

The takeaway is practical. Prioritize an eye-clean stone, meaning one with no inclusions visible to the naked eye at normal viewing distance. In step cuts that usually means paying more attention to clarity than you would for a brilliant, and many buyers are most comfortable in the VS range or better for an asscher. Our guide to VVS vs VS clarity explains where the eye-clean line actually falls and where paying up stops being visible. Color is the same story: the open table also shows body color more readily, so choose a color grade you are happy to look straight down into, and always judge clarity and color from the actual stone or its images, not from the grade alone.

The asscher and the emerald are the two step cuts most people compare, because they share their whole personality: the same parallel step facets, the same open table, the same mirror-like flash, and the same need for good clarity and color. The decision between them is almost entirely about shape. An asscher is square, near a 1.00 ratio, with the windmill pattern radiating from the center. An emerald is a rectangle, commonly around 1.30 to 1.50, with the flashes running down its length. Pick the asscher if you want a compact, symmetrical, architectural stone; pick the emerald if you want length that stretches the finger.

Neither is better; they suit different hands and different tastes. If you already know you want the step-cut look and are only deciding between square and rectangular, the asscher is the quieter, more geometric of the two, and the emerald is the more elongated and classic.

The asscher and the princess are the other common comparison, and it trips people up because both are square. The difference is the faceting, and it changes everything about how they look. A princess is a brilliant cut: hundreds of small triangular and kite-shaped facets that throw off bright, fiery sparkle and hide inclusions well. An asscher is a step cut: broad mirror flashes, an open geometric pattern, and no place for inclusions to hide. One looks lively and modern, the other looks calm and architectural.

There is also a durability difference worth knowing. A princess keeps sharp, uncropped 90-degree corners, which are the most vulnerable points on the stone and want protective prongs or a setting that shields them. An asscher crops its corners, so it has no exposed points and is the more forgiving of the two to wear day to day. If you love bright sparkle and do not mind protecting the corners, the princess is your cut. If you love clean lines, mirror flash, and a robust stone, the asscher is.

An asscher works beautifully in a Lab Grown Diamond, and for the asscher specifically the reason is more than aesthetic. Because the open step cut shows clarity and color so plainly, a higher-clarity, higher-color stone matters here more than it does for a brilliant. Lab Grown Diamonds make that easier to reach, since a given clarity and color grade is generally more attainable than in a mined stone (Source: StoneAlgo, 2026). A Lab Grown Diamond is a real diamond, chemically and physically identical to a mined one, the same pure carbon and the same Mohs 10 hardness, so nothing about the cut or the look changes with the origin.

Buy the asscher because you love how it looks, not as an investment. A diamond is a love piece, not a financial instrument, and the "diamonds hold their value" line is a myth worth ignoring. What actually protects you is the certificate. On a grading report an asscher is described by its geometry, for example "Square Emerald Cut" or "Cut-Cornered Square Step Cut," not by the trade name "asscher," so read the shape description and the measurements and confirm the report number on the issuing lab's own website. For a Lab Grown Diamond, IGI and GCAL still issue full 4C-style reports; GIA has graded Lab Grown Diamonds on Premium and Standard descriptive tiers since October 1, 2025 (Source: GIA, 2025-10-01). Check the girdle for the laser inscription, including the "LG" marking that identifies a Lab Grown Diamond.

An asscher cut diamond suits someone drawn to clean geometry and understatement rather than maximum sparkle. It reads as vintage and architectural at once, with a quiet, deliberate flash instead of fire, so it appeals to a buyer with a taste for symmetry and restraint. Because it faces up compact and deep rather than large and spread, it favors someone who wants presence and dimension over the biggest possible outline for the weight. And because it is uncommon next to rounds and ovals, it suits a buyer who would rather not wear the same shape as everyone else. If a step cut appeals but you want square rather than elongated, the asscher is the natural choice, and if you are torn between shapes generally, the diamond shapes guide sets the options side by side.

Stienhardt is a New York City jeweler that sources Lab Grown Diamonds and hand-sets and finishes them in NYC, selling direct, so we own and inspect every stone we sell and hand you its independent report rather than just drop-ship it. For a step cut that matters, because the whole point of an asscher is an eye-clean, open, honest stone, and that is something you confirm by looking, not by trusting a label. Viewings are by appointment.

So the advice we keep repeating applies to our own work too: read the graded report behind any asscher sold under a cut name, ours included, and confirm the shape, the measurements, and the report number for yourself. The trade name tells you what a seller calls the cut. The report tells you what you are actually buying.

If you would rather judge a stone in person, we show by appointment in New York. Book a viewing.