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The stone guide
Understanding Your Stone
This guide explains lab-grown diamonds and moissanite so you can compare their properties. Each approved individual lab-grown center or primary diamond of 0.50 ct or more includes an IGI grading report. Other documentation and its scope are stated on the product page or approved specification.
Where to start
The Four Things That Define a Diamond
Lab-grown and mined diamonds can be assessed against the same four criteria — color, cut, clarity, and carat. Understanding these lets you make a smart choice rather than just buying the biggest number. Every finished Signora piece includes a Signora Jewelry Certificate. Each approved individual lab-grown center or primary diamond of 0.50 ct or more also includes an IGI grading report; other documentation and its scope are stated on the product page or approved specification. Learn how to read the exact document in our IGI grading report guide.
Color
How white or tinted
Cut
How it handles light
Clarity
Inclusions and flaws
Carat
Weight, not size
The 4Cs · Color
Color — The Less, The Rarer
Diamonds are graded on a D–Z scale, where D is completely colorless and Z shows visible yellow or brown tint. The absence of color is rarer and commands a higher price — but beyond H, the difference is almost invisible to the naked eye.
D–F
Colorless
G–H
Near colorless
I–J
Near colorless
K–Z
Faint to light
G–H
RecommendedVirtually white in most settings
Signora note
Best value — our recommendation
Signora tip
For most settings, G–H color gives you the look of a D at a fraction of the price. In yellow or rose gold, I–J can look completely white — the warm metal masks any tint.
The 4Cs · Cut
Cut — The Most Important C
Cut is not the shape of the diamond — it is how well the facets are proportioned, polished, and aligned to reflect light. A poorly cut diamond looks dull no matter how large or clear it is. A well-cut diamond of modest size will outshine a large, poorly cut one every time.
Poor
Fair
Good
Very Good
Excellent
Cut quality is a major driver of sparkle and brilliance. Compare the grade, proportions and actual light return together.
Anatomy of the cut
Table — the large flat facet on top
Crown — the angled section above the girdle
Girdle — the widest edge, where the stone is held
Pavilion — the lower cone that returns light
Culet — the tiny point at the very bottom
Proportions affect how light enters, reflects, and exits the stone.
Signora tip
When an independent cut grade is stated for a stone, Excellent and Very Good are useful reference points. A round brilliant with an Excellent cut grade is a benchmark of sparkle; for other shapes, compare the proportions and finish stated for that exact stone.
The 4Cs · Clarity
Clarity — Imperfections That Are Mostly Invisible
Clarity measures inclusions (internal characteristics) and blemishes (surface marks) in a diamond. Almost all diamonds have them — the question is whether they are visible to the naked eye and whether they affect the stone's beauty or structural integrity.
◇
FL / IF
VVS1–VVS2
VS1–VS2
Sweet spot
SI1–SI2
I1–I3
Very Slightly Included VS1–VS2
Minor inclusions, not visible to the naked eye.
Signora tip
When an independent clarity grade is stated, VS1–VS2 can be a useful balance between an eye-clean appearance and price. SI1 can also be eye-clean; ask us to review the exact stone details before you buy.
The 4Cs · Carat
Carat — Weight, Not Size
Carat refers to the weight of a diamond, not its physical dimensions. A well-cut 1.9ct diamond can look as large as a 2.0ct — so buying just below a round number (1.9ct instead of 2.0ct, 0.9ct instead of 1.0ct) is one of the smartest ways to save without any visible difference.
The physical size also depends on the shape — a 1ct oval appears larger face-up than a 1ct round, because ovals have a larger surface area for the same weight.
0.5ct
≈ 5.2mm
1.0ct
≈ 6.5mm
1.5ct
≈ 7.4mm
2.0ct
≈ 8.2mm
2.5ct
≈ 8.8mm
3.0ct
≈ 9.4mm
4.0ct
≈ 10.2mm
Approximate face-up diameter for a round brilliant. Tap a stone to compare.
Signora tip
Our rings are available from 1.0ct to 4.5ct. For an engagement ring, 1.5ct–2.0ct is the most popular range — substantial without being overstated.
Shape
Shape — The Look That Defines the Ring
Shape is the physical outline of the stone as seen from above. It is often (incorrectly) called cut — but shape and cut are different things. Shape is a style choice; cut is a quality grade. Each shape has its own character.
Round Brilliant
The most brilliant shape. Maximizes sparkle. The classic choice.
Oval
Elongates the finger. Larger face-up appearance per carat. Romantic and modern.
Princess Cut
Bold square outline. Strong geometry, excellent brilliance. Contemporary.
Cushion
Soft rounded corners. Vintage warmth with modern appeal.
Pear
Unique teardrop silhouette. Slimming on the finger. Elegant and distinctive.
Emerald
Step-cut facets. Sophisticated hall-of-mirrors effect. Understated luxury.
Radiant
Brilliant-cut in a rectangular shape. Maximum sparkle in a longer outline.
Marquise
The most elongating shape. Dramatic and vintage-inspired.
Asscher
Square step-cut. Deep, geometric, architectural. A statement piece.
Heart
The most romantic shape. Best in 1ct+ for the outline to read clearly.
Signora tip
If you want the stone to look as large as possible for your budget, choose oval, pear, or marquise — their elongated outlines appear bigger than a round of the same carat weight. Compare proportions and visual character in the full diamond shape guide.
Beyond the 4Cs · Fluorescence
Fluorescence — The Glow Under UV
Some diamonds emit a soft glow — usually blue — under ultraviolet light. That reaction is called fluorescence, and it is graded on its own scale, separate from the 4Cs. In everyday lighting it is generally invisible, which is why it is one of the least understood lines on a grading report.
None
No reaction
Safe default
Faint
Barely detectable
Safe default
Medium
Noticeable under UV
Strong
Clear blue glow
Very Strong
Pronounced glow
The fluorescence scale, from no reaction under UV light to a pronounced glow.
Signora tip
None to Faint is a useful reference point. Medium blue fluorescence can make a near-colorless stone face up slightly whiter, while Strong fluorescence can — rarely — give a stone a hazy look. When an external grading report is included for the exact stone, check that report for its recorded fluorescence.
Beyond the 4Cs · Finish
Polish & Symmetry — The Finishing Touches
Polish describes how smoothly each facet surface has been finished; symmetry describes how precisely those facets align and mirror one another. Both can be graded on the same five-step scale — Excellent, Very Good, Good, Fair, Poor — and may appear on an external grading report when one is included for the exact stone.
The finish scale — Excellent to Poor
Excellent — facets are flawlessly smooth and precisely aligned — nothing interrupts the light
Very Good — minute deviations only a grader would find, with no visible effect on sparkle
Good — small irregularities visible under magnification that can slightly soften brilliance
Fair — misaligned or unevenly finished facets begin to blur the play of light
Poor — visible finishing faults that noticeably dull the stone
Cut grade gets the attention, but polish and symmetry are the craftsmanship behind it — the final refinements that let a well-proportioned stone actually deliver its sparkle.
Signora tip
Look for Excellent or Very Good in both polish and symmetry. Below that, imperfect facets can blur the sharp flashes of light that make a diamond sparkle — a difference you may notice even when the cut grade looks good on paper.
Lab diamond vs moissanite
Which Stone Is Right for You?
Signora designs may offer lab-grown diamonds or moissanite, each with different optical properties. Check the product page for the stone offered. Each approved individual lab-grown center or primary diamond of 0.50 ct or more includes an IGI grading report; other documentation and its scope are stated on the product page or approved specification.
Diamond
Lab-Grown Diamond
Gemstone
Moissanite
Composition
Pure carbon
Silicon carbide
Hardness (Mohs)
10 — the hardest known material
9.25 — excellent durability
Brilliance
High (refractive index 2.42)
Very high (refractive index 2.65)
Light dispersion
White sparkle
Colorful "fire" — rainbow flashes
External report
IGI for approved individual center or primary diamond 0.50 ct+
Custom selection · scope confirmed before approval
Price
Higher
Lower — more accessible
Origin
Grown in a controlled laboratory
Lab-created
Best for
Those who want a diamond, full stop
Those who want brilliance at better value
Moissanite's higher refractive index means it throws more colorful light ("fire") than a diamond. The choice comes down to material, appearance and budget; use the focused diamond versus moissanite guide for a deeper comparison.
Signora tip
If you are unsure, book a consultation with Himmat. He can show you both side by side and help you choose based on your preference, occasion, and budget.
Pairing stones with metals
Which Metal Suits Your Stone?
The metal you choose affects how the stone looks as much as the stone itself. Here is a quick guide.
Signora tip
Rose gold adds warmth and can complement many stone colors. Platinum is dense, naturally white and commonly chosen for long-term settings.
Lab-grown vs natural
Lab-Grown vs Natural, Honestly
A lab-grown diamond and a natural diamond are the same crystal — pure carbon, chemically, physically, and optically identical. The only difference is where that crystal formed. Here is the honest version, without the marketing.
What is the same, what is different
Same crystal — both are crystallised carbon with identical hardness, brilliance, and fire — indistinguishable to the eye
Different origin — a natural diamond formed deep in the earth over geologic time; a lab-grown diamond crystallises in a matter of weeks in a controlled growth chamber
Same grading — both are graded against the same 4Cs — color, cut, clarity, and carat — by independent laboratories
Different price — a lab-grown diamond costs meaningfully less than a natural stone of the same grade, which is why budgets go further on cut and size
Neither is an investment — diamonds of either origin should be bought for beauty and meaning, not resale — neither is a financial asset
Many Signora designs offer lab-grown diamonds; the exact stone origin is identified on each product page. Natural diamonds may be requested for a custom commission. Compare origins in the lab-grown versus natural guide, then follow the making journey in From Seed to Signora.
Questions, answered
Diamond & Stone FAQ
The questions we hear most often in consultations — answered plainly.
Is a lab-grown diamond a real diamond?
Yes. A lab-grown diamond is crystallised carbon with the same fundamental chemical, physical and optical properties as a natural diamond. It can be assessed against the same 4Cs. Each approved individual lab-grown center or primary diamond of 0.50 ct or more includes an IGI grading report; other documentation and its scope are stated on the product page or approved specification.
What certificate do Signora diamonds come with?
Every finished piece includes a Signora Jewelry Certificate recording the piece and selected materials. Each approved individual lab-grown center or primary diamond of 0.50 ct or more also includes an IGI grading report. Other independent documentation and its scope are stated on the product page or approved specification.
Which of the 4Cs matters most on a budget?
Start with cut and actual light return. Then compare color and clarity stone by stone, because “eye-clean” appearance depends on the inclusion, lighting, viewing distance and your preference. Use the remaining budget for the size that suits the design.
What is diamond fluorescence?
Fluorescence is a soft glow — usually blue — that some diamonds show under ultraviolet light, graded from None to Very Strong. None to Faint is a useful reference point; Strong fluorescence can rarely cause a hazy look. When an external grading report is included for the exact stone, check it for the recorded fluorescence.
Are D-color stones worth it under 1 carat?
Usually not. Below 1 carat, an eye-clean stone in G color or better can look very similar to a D face-up; where an external grading report is included, it records the exact color grade. Paying for what the eye can actually see is exactly the thinking behind the Signora Standard.
Do lab-grown diamonds test as diamonds?
Yes — a lab-grown diamond reads as diamond on a standard thermal tester, because it is diamond. Moissanite can also pass a basic thermal tester, so jewelers use additional testing to distinguish the two.
Still deciding?
Talk to the Person Who Makes Your Ring
Book a free 20–30 minute consultation with Himmat, Signora's founder and designer. No obligation — just honest advice about what will look best for your preferences and budget.