GCAL Diamond Certification Guide

The Gem Certification & Assurance Lab (GCAL) provides a range of services for the gem and jewelry trade including grading and certification of natural diamonds, lab grown (synthetic) diamonds, diamond cut analysis, colored stone and pearl identification, precious metals analysis, as well as video and photography. GCAL is also in the appraisal business and offer diamond jewelry reports and valuation.
GCAL was founded by Donald Palmeiri in 2001 and operates out of a single location at 580 Fifth Avenue in New York. The lab is certified for ISO 17025, the highly respected international quality management system. ISO certification is an impressive thing for any business to achieve.
Simon G. MR1811 Passion Halo Diamond Engagement Ring
Simon G. MR1811 Passion Halo Diamond Engagement Ring
For the purposes of this article, we will focus on GCAL’s diamond evaluation services, and in particular their cut grading system. Most gem labs follow closely the GIA model in assessing clarity and color. Cut grading methodologies vary widely among labs, with some having no cut grade at all. Even today, GIA only grades cut on round brilliants and is known to be a very broad and forgiving system. With the recent introduction of their 8X cut grade, GCAL seems to be making a strong bid in this key area of diamond assessment.

Cut Grading

GCAL notes that over 50% of round GIA diamonds are graded Excellent for cut (their highest grade), yet many of them have significant cutting or light performance deficits. GCAL states that only 1% of GIA Excellent diamonds would receive their new 8X™ cut grade.
GCAL Natural Diamond Certificate
GCAL Natural Round Diamond Certificate - Click to enlarge
GCAL states that their new grading system encompasses all aspects of diamond cut quality assessment.
  • Polish
  • External Symmetry
  • Proportions
  • Optical Brilliance
  • Fire
  • Scintillation
  • Optical Symmetry
  • Hearts and arrows

Polish and Symmetry

Virtually all diamond labs grade these physical attributes. The degree to which the cutter achieves a mirror finish on all the facets, and the degree to which contiguous facets are in alignment (also referred to as ‘meet-point’ symmetry).


This is a critical factor in cut quality, ensuring that the basic build of the diamond is capable of enabling light to be fully reflected and refracted. These are the proportion ranges that GCAL considers Ideal:
  • Table % : 54.0% - 58.0%
  • Depth % : 59.8% - 62.2%
  • Crown Angle : 34.0 0 - 35.00
  • Pavilion Angle : 40.6 0 - 41.00
  • Lower Girdle Facet Length : 75% - 80%
  • Star Length : 45% - 55%
  • Girdle Thickness : THIN TO SLIGHTLY THICK, faceted
  • Culet Size : NONE - VERY SMALL

Optical Brilliance, Fire, and Scintillation (Light Performance)

GCAL defines the term “optical brilliance” as the overall return of white light to the viewer. This is generally referred to by other labs simply as brightness or light return. Fire is the result of dispersion of white light into it’s spectral colors, and is visible when a diamond is in motion in a fire friendly lighting environment. Scintillation refers to the sparkle of the diamond in motion. This effect relies on contrast to cause facets to alternately blink on and off.

Optical Symmetry and Hearts and Arrows

The last two factors relate to craftsmanship and the precision of the faceting; optical symmetry and hearts and arrows patterning. Interestingly, GCAL separates these two properties which most labs refer to as one in the same. Both are aspects of patterning that indicate the precision and uniformity of facet shapes and alignment. The hearts and arrows image used by GCAL is the familiar red and white image, while the optical symmetry image looks very similar to ASET with red, green and blue components.
GCAL Optical Symmetry
GCAL Optical Symmetry

Cut grading of Fancy Shapes

GCAL offers cut grading on two other shapes besides round brilliant; Ovals and Princess cuts. A similar assessment is made, with the substitution of Shape Aesthetics for optical symmetry and hearts and arrows.
GCAL Oval Fancy Shape Certificate
GCAL Oval Fancy Shape Certificate - Click to enlarge


Each diamond report also contains a magnified photo of the diamond (GCAL calls them “photomicrographs”). This can be helpful in showing internal characteristics that might be present.

Laser Inscription

Laser inscription is included on most GCAL diamond certificates, both natural and lab grown. Typically the lab report number will be inscribed and a photo of the inscription contained on the report. In the case of lab grown diamonds the letters LG will precede the number and LAB GROWN will be inscribed on the girdle on the opposite side.


Gemprint® is an interesting technology that shines a laser into a diamond and makes of map of the reflection patterns. It serves as a ‘fingerprint’ of the diamond that accounts for both the nuances of faceting and to some extent anyway, inclusions. A diamond’s Gemprint can be compared against itself to confirm identification, or compared to a database to find a match.
You can register your Gemprint and enter it into an international database. Some insurance companies offer a discount for diamonds in the Gemprint registry as it makes recovery of stolen gems more likely. GCAL is unique in offering this service.
GCAL Gemprint
GCAL Gemprint

Lab Grown Diamond Reports

GCAL provides identification and grading for lab grown diamonds as well as natural, Earth mined diamonds. They offer a full grading report including light performance and hearts and arrows, as well as scaled down versions including an “Express” report.
GCAL Lab Grown Diamond Certificate
GCAL Lab Grown Diamond Certificate - Click to englarge

Gemstone and Pearl Reports

GCAL offers identification as well as full grading reports on gemstones and pearls. A full report on a gemstone will include a graph of its UV behavior, a photo of the gem, and a description of its cut quality. A pearl report will include a description of its surface quality and luster.
GCAL Colored Gemstone Certificate
GCAL Colored Gemstone Certificate - Click to enlarge
GCAL Pearl Jewelry Certificate
GCAL Pearl Jewelry Certificate - Click to enlarge

GCAL Jewelry Appraisals

Leveraging the data in the Jewelry Market Monitor, the ‘blue book’ of wholesale gemstones and jewelry published by its founder since 1982, GCAL performs appraisals on finished jewelry pieces and can tailor the type of appraisal to the client’s intended purposes. Whether it is Retail Replacement value for insurance purposes, Fair Market Value for charitable donation, or Marketable Cash Value for legal and personal settlements, GCAL can accommodate.
GCAL Jewelry Appraisal Report
GCAL Jewelry Appraisal Report - Click to englarge

Certificate vs Report – A Distinction without a Difference?

Prominent in GCAL’s marketing is the claim that their grading reports are guaranteed. They point out specifically that this distinguishes their ‘certificate’ from grading reports issued by AGS and GIA. However, the guarantee is very generalized and their ‘cash back’ claims to do not specify whether they are offering to refund the fee that was paid for the certificate or any damages that might have been incurred by an error on their part. If these issues are important to you, it will be best to have a detailed discussion with GCAL and/or get those details in writing.

Other GCAL Services and Specialties

On the strength of company founder Donald Palmeiri and his extensive experience in identification and valuation of diamonds and gemstones, GCAL serves as a consultant and expert in court cases including insurance and law enforcement cases. They also perform inventory audits and risk assessment for insurance companies and businesses, as well as consulting on damage and restoration, helping tradespeople to work through things like the calculus of recutting diamonds.


GCAL is a small, high quality gemological laboratory with all operations in one location in the Diamond District of New York. They bring extensive experience and technical knowledge to providing a very wide range of services for diamonds, colored gemstones, pearls and fine jewelry. Their recent foray into comprehensive cut grading is indicative of their desire to remain on the leading edge of the industry.
They cater to the diamond and jewelry trade and submissions must be on company letterhead. Individuals who would like to access their services need to go through a member of the jewelry trade.

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