Diamond Prices
Read more
Diamond grading tools: the instruments diamond traders and gemologists use
From tweezers to the microscope: what each tool does, who needs it, and the kit we’d put together for you.
Short answer: to look at a diamond properly you need four things: diamond tweezers, a 10× triplet loupe, a daylight lamp and a lint-free cloth. Traders add a carat scale, a caliper, a UV light and a tester. Gemologists add a microscope, a refractometer and a polariscope. Labs use grading machines on top.
Free tool · 5 minutes
Is your diamond real? 6 home tests, no tools needed
Rule out glass, cubic zirconia and other common imitations in five minutes. A stone that passes isn’t proven real: only a gem lab can confirm that.
Start the 6 tests →Interactive
Build your kit
Who are you? The tools you need light up below, with a rough budget.
Your kit
Pick one above.
Start small: a good loupe and tweezers beat a drawer of cheap gadgets.
The tools
The 12 diamond tools, and what each one is for
Grouped the way a trader’s desk is: handle, look, sort, measure, test.
Favorite Swiss-made diamond lock tweezers · I.David Antwerp ↗HandlingDiamond tweezers
Skin oils dull a diamond, and a smooth stone slips easily. Grooved, locking tweezers hold it safely. Pick a size that fits the stone: fine tips for small stones, wider ones for a few carats.
Our tip: nothing scratches a diamond, but steel can still mark a perfect polish. For your best stones we like soft-tip “pearl” tweezers.
Best brands: Favorite (Swiss made) · Dumont
Our pick: Favorite Swiss-made diamond lock tweezers ↗
GIA Gem Cloths · GIA ↗HandlingLint-free cloth
Microfibre takes off oils and dust without scratching the setting. Washable, and the simplest way to bring back the sparkle before you look.
Best brands: GIA Gem Cloth · Selvyt
Our pick: GIA Gem Cloths ↗
H. Schneider 10× loupe · I.David Antwerp ↗Viewing10× triplet loupe
The standard for clarity. Three lenses keep the image sharp to the edges. 10× is the grading norm: stronger loupes show less and blur more.
Best brands: Schneider (Germany) · Zeiss optics
Our pick: H. Schneider 10× loupe ↗
Dazor 2-tube daylight lamp · I.David Antwerp ↗ViewingDaylight lamp
A neutral 5500–6500 K light. Warm light hides yellow, blue light hides brown. The white Dazor arm lamp is on most traders’ desks in Antwerp.
Best brands: Dazor · Eickhorst
Our pick: Dazor 2-tube daylight lamp ↗
I.David diamond scoops ↗SortingDiamond scoop
Moves small stones from paper to tray to scale without losing any. Stainless steel lasts for years.
Where we buy: I.David (Antwerp)
Our pick: I.David diamond scoops ↗
GIA Diamond Sorting Pads · GIA ↗SortingSorting pad
A matte, non-reflective white surface for comparing colour and spreading a parcel. Many show the GIA colour and clarity scales.
Best brands: GIA sorting pads
Our pick: GIA Diamond Sorting Pads ↗
I.David Super Sieve Set ↗SortingSieve set
Sorts small diamonds by size, about 1 to 4.5 mm, a whole parcel at a time. Every manufacturer has one.
Where we buy: I.David (Antwerp)
Our pick: I.David Super Sieve Set ↗
Sartorius carat scale, 600 ct / 0.001 ct · I.David Antwerp ↗MeasuringCarat scale
Accurate to 0.01 ct or better, with a level bubble and a test weight. Prices jump at 0.50, 1.00 and 2.00 ct, so a hundredth matters. Sartorius is what we use.
Best brands: Sartorius · Mettler Toledo
Our pick: Sartorius carat scale, 600 ct / 0.001 ct ↗
Presidium Electronic Gemstone Gauge · Presidium ↗MeasuringDigital caliper
Measures diameter and depth in millimetres, so you can check proportions and compare with the lab report.
Best brands: Presidium · Leveridge
Our pick: Presidium Electronic Gemstone Gauge ↗
GIA UV Lamp and Viewing Cabinet · GIA ↗MeasuringLong-wave UV light
Shows fluorescence, usually blue, sometimes white, yellow or green. A grading factor, and a clue when telling stones apart.
Best brands: GIA · KRÜSS UV240
Our pick: GIA UV Lamp and Viewing Cabinet ↗
Presidium Multi Tester III · Presidium ↗TestingDiamond tester
Rules out glass and cubic zirconia. A multi-tester also catches moissanite. No tester proves a diamond is natural. Which tester? →
Best brands: Presidium · Ceres
Our pick: Presidium Multi Tester III ↗
GIA Gemolite NXT Microscope · GIA ↗ViewingGem microscope
30× and more, with dark-field light. Shows inclusions and growth patterns that help separate natural from lab-grown, in trained hands.
Best brands: GIA Gemolite · KRÜSS
Our pick: GIA Gemolite NXT Microscope ↗Coloured gemstones
The gemologist’s bench: 6 instruments for coloured stones
Rubies, sapphires and emeralds have more look-alikes than diamonds. These are the classic tools gemologists use to tell them apart.
GIA Duplex II Refractometer · GIA ↗OpticsRefractometer
Measures how much a stone bends light (its refractive index). Each gem has its own number, so it’s the gemologist’s first ID test.
Best brands: GIA Duplex II · KRÜSS
Our pick: GIA Duplex II Refractometer ↗
GIA Polariscope · GIA ↗OpticsPolariscope
Two crossed polarising filters. Shows if a stone is singly or doubly refractive, and reveals strain that can point to glass or a synthetic.
Best brands: GIA · KRÜSS
Our pick: GIA Polariscope ↗
KRÜSS Polariscope PK14-LED · KRÜSS ↗OpticsConoscope
A small glass sphere used with the polariscope. It shows the interference figure, telling uniaxial gems (like ruby) from biaxial ones (like peridot).
Best brands: KRÜSS · GIA
Our pick: KRÜSS Polariscope PK14-LED ↗
KRÜSS London Dichroscope LD10 · KRÜSS ↗ColourDichroscope
Shows the two or three colours some gems display from different angles. Cheap, and in use since the 19th century.
Best brands: KRÜSS London (Gem-A)
Our pick: KRÜSS London Dichroscope LD10 ↗
KRÜSS Hand Spectroscope HS1504 · KRÜSS ↗ColourSpectroscope
Splits light into a spectrum and shows the dark lines a gem absorbs. Some gems, and some treatments, leave a signature.
Best brands: KRÜSS · GIA
Our pick: KRÜSS Hand Spectroscope HS1504 ↗
Sartorius density scale · I.David Antwerp ↗WeightHydrostatic balance
Weighs a stone in air and in water to find its density (specific gravity). A fake rarely matches the real gem’s number. Density calculator →
Best brands: Sartorius · KERN
Our pick: Sartorius density scale ↗How to
Use a loupe like a trader, in 5 steps
- Clean the stoneUse the cloth. Fingerprints look like inclusions.
- Loupe close to your eyeRest your hand on your cheek.
- Bring the stone inHold it in tweezers and move it toward the loupe until it’s sharp, about 2.5 cm away.
- Brace both hands togetherThe stone and the loupe then move as one.
- Table first, then tiltLook straight through the top, then tilt slowly to see the sides and the girdle.
Seeing an inclusion doesn’t tell you the grade: clarity grades also depend on size, number, position and colour of inclusions. That’s what a lab report is for.
Search: “diamond grading machine”
Grading machines
Where the trade has moved in the last ten years.
GIA iD100 · GIA ↗Lab-grown screeners
Pass natural diamonds in seconds and flag possible lab-grown stones for a lab.
Examples: GIA iD100 · De Beers SynthDetect · HRD D-Screen
Our pick: GIA iD100 ↗Cut and proportion scanners
Measure every facet and angle in 3D, and help planners decide how to cut a rough.
Examples: Sarine · OctoNus Helium
Automated sorting
Sort melee by size, colour and type in bulk. Used by manufacturers and labs for small stones.
Want to look through our loupe? Come to our Antwerp office and our team shows you how traders grade a stone. Book a visit →
Want to learn grading properly? The best diamond grading schools →
FAQ
Quick answers
What magnification is used to grade diamonds?
10×. Clarity grades are defined at 10×, so the loupe is the reference, even in labs. Microscopes help find and photograph inclusions, but the grade is set at 10×.
Can I grade a diamond myself?
You can check it. A reliable grade needs master stones, controlled light and years of training. That’s what a lab report is for.
What’s the best loupe for diamonds?
A 10× triplet with a black housing and a wide field of view. Higher magnification isn’t better for grading.
What tools do I need to check a diamond at home?
A 10× loupe, a lint-free cloth and good daylight. Add a tester if you want to rule out simulants. For “is it real?”, start with our 6 home tests.
Which machine tells natural from lab-grown diamond?
Screening machines like the GIA iD100 or De Beers SynthDetect pass natural stones and flag the rest. A flagged stone goes to a gem lab for a final answer.
What tools do gemologists use for coloured stones?
A refractometer, a polariscope, a dichroscope, a spectroscope, a hydrostatic balance and a microscope. Together they identify the gem and spot most treatments and synthetics.