The Four C's of a Diamond
How Do I Determine My Ring Size?
Diamond Care
Platinum versus White Gold
What is Moissanite?
What are the qualities of a diamond?
What is "pttw"? What does it stand for?
What is Cubic Zirconia (CZ)?
Cubic Zirconia (CZ) versus Diamond
Birthstones and their significance
Converter Chart: mm to inch
Carats to Millimeters Conversion Chart for Round Diamonds
Jewelry Stamping: Hallmarks
Common Gemstone Cuts
American Gem Trade Association (AGTA) Enhancement Codes
The Four C's of a Diamond: Color, Clarity, Cut and Carat weight
Diamonds professionals use the following four factors to describe and classify diamonds: color, clarity, cut and carat weight. When taken together, they help in evaluating the finished diamonds you buy. That's why they are often called value factors.
Color
Diamonds in the normal color range are graded by their relative lack of color. A diamond that is said to have "fine color" has little or no visible coloration. The less color, the higher the value. Diamonds outside the normal color range are called fancy-colored and come in about any color you can imagine.
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Clarity
Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of clarity characteristics. Blemishes include scratches and nicks on a diamond’s surface. Inclusions are on the inside (some might break the surface of the stone, but they are still considered inclusions). Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they’re located, they might still be there after the stone has been cut and polished.
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Cut
The cut of a diamond as a value factor, refers to its proportions, symmetry and finish. It is not to be confused with its shape.
Proportion refers to the angles and relative measurements of a polished diamond. More than any other feature, proportions determine a diamond's optical properties. Studies have shown that table size, crown angle, and pavilion depth have a dramatic effect on a diamond's appearance.
Symmetry is a grading term for the exactness of shape and placement of facets. Variations in symmetry include off-center culets and tables, poor facet alignment, misshapen facets, out-of-round girdles, and wavy girdles.
The finish is the quality of a diamond’s polish, the condition of its girdle, and the precision of the cut.
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Diamond Shapes
Shapes other than the standard round brilliant shown above are called fancy shapes or fancy cuts. Their names are based on their shapes. The best known are the heart, marquise, pear-shaped cut, emerald-cut, oval, and radiant.
    
Click here to see larger pictures of diamonds.
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Carat Weight
Diamonds are weighed to a thousandth (0.001) of a carat and then rounded to the nearest hundredth, or point. Over a carat, diamond weights are usually expressed in carats and decimals. A 1.03 ct. stone, for example, would be described as "one point oh three carats," or "one oh three." A diamond that weighs 0.83 ct. is said to weigh "eighty-three points," or an "eighty-three pointer." According to the 1907 international standard, one carat is equivalent to 0.2 gram.
The cumulative diamond weight of a piece of jewelry that includes several diamonds is measured in TCW (total carat weight) or pttw (points total weight) or Carats Total Weight (Carat TW). One TCW/Carat TW is equal to 100 pttw. For example, a diamond pendant with 83 pttw dia will have a total diamond weight of 0.83 carat or 0.83 TCW/Carat TW.
Some weights are considered "magic sizes" – half carat, three-quarter carat, carat. Visually, there’s little difference between a 0.99 ct. diamond and one that weighs a full carat. But the price differences between the two can be significant.
Many people would like to understand carat sizes in real terms. Here are some approximate, sample carat-weight to diameter-widths for round cut diamonds in popular sizes:
0.25 carat = 4.1 mm 0.50 carat = 5.2 mm
0.75 carat = 5.8 mm 1.00 carat = 6.5 mm
| Carats |
|
Diameter (mm) |
|
Carats |
|
Diameter (mm) |
|
|
|
|
|
|
|
| .005 |
|
1.0 |
|
1.25 |
|
7.0 |
|
|
|
|
|
|
|
| .0067 |
|
1.15 |
|
1.33 |
|
7.2 |
|
|
|
|
|
|
|
| .01 |
|
1.3 |
|
1.50 |
|
7.4 |
|
|
|
|
|
|
|
| .015 |
|
1.5 |
|
1.60 |
|
7.6 |
|
|
|
|
|
|
|
| .02 |
|
1.7 |
|
1.75 |
|
7.8 |
|
|
|
|
|
|
|
| .025 |
|
1.8 |
|
1.90 |
|
8.0 |
|
|
|
|
|
|
|
| .03 |
|
2.0 |
|
2.00 |
|
8.2 |
|
|
|
|
|
|
|
| .035 |
|
2.1 |
|
2.15 |
|
8.4 |
|
|
|
|
|
|
|
| .04 |
|
2.2 |
|
2.25 |
|
8.6 |
|
|
|
|
|
|
|
| .05 |
|
2.4 |
|
2.50 |
|
8.8 |
|
|
|
|
|
|
|
| .06 |
|
2.5 |
|
2.65 |
|
9.0 |
|
|
|
|
|
|
|
| .07 |
|
2.7 |
|
2.85 |
|
9.2 |
|
|
|
|
|
|
|
| .08 |
|
2.8 |
|
3.00 |
|
9.4 |
|
|
|
|
|
|
|
| .09 |
|
2.9 |
|
3.15 |
|
9.6 |
|
|
|
|
|
|
|
| .10 |
|
3.0 |
|
3.35 |
|
9.8 |
|
|
|
|
|
|
|
| .11 |
|
3.1 |
|
3.50 |
|
10.0 |
|
|
|
|
|
|
|
| .12 |
|
3.2 |
|
3.75 |
|
10.2 |
|
|
|
|
|
|
|
| .14 |
|
3.3 |
|
4.00 |
|
10.4 |
|
|
|
|
|
|
|
| .15 |
|
3.4 |
|
4.25 |
|
10.6 |
|
|
|
|
|
|
|
| .16 |
|
3.5 |
|
4.50 |
|
10.8 |
|
|
|
|
|
|
|
| .17 |
|
3.6 |
|
4.75 |
|
11.0 |
|
|
|
|
|
|
|
| .18 |
|
3.7 |
|
5.00 |
|
11.2 |
|
|
|
|
|
|
|
| .20 |
|
3.8 |
|
5.25 |
|
11.4 |
|
|
|
|
|
|
|
| .22 |
|
3.9 |
|
5.50 |
|
11.6 |
|
|
|
|
|
|
|
| .23 |
|
4.0 |
|
5.75 |
|
11.75 |
|
|
|
|
|
|
|
| .25 |
|
4.1 |
|
5.81 |
|
11.8 |
|
|
|
|
|
|
|
| .30 |
|
4.2 |
|
6.00 |
|
11.9 |
|
|
|
|
|
|
|
| .33 |
|
4.4 |
|
6.25 |
|
12.1 |
|
|
|
|
|
|
|
| .35 |
|
4.5 |
|
7.00 |
|
12.5 |
|
|
|
|
|
|
|
| .38 |
|
4.6 |
|
7.50 |
|
12.85 |
|
|
|
|
|
|
|
| .40 |
|
4.8 |
|
7.75 |
|
13.00 |
|
|
|
|
|
|
|
| .43 |
|
4.9 |
|
8.00 |
|
13.1 |
|
|
|
|
|
|
|
| .47 |
|
5.0 |
|
8.23 |
|
13.25 |
|
|
|
|
|
|
|
| .50 |
|
5.2 |
|
8.50 |
|
13.4 |
|
|
|
|
|
|
|
| .60 |
|
5.4 |
|
8.75 |
|
13.5 |
|
|
|
|
|
|
|
| .63 |
|
5.5 |
|
9.00 |
|
13.65 |
|
|
|
|
|
|
|
| .65 |
|
5.6 |
|
9.20 |
|
13.75 |
|
|
|
|
|
|
|
| .75 |
|
5.8 |
|
9.75 |
|
14.0 |
|
|
|
|
|
|
|
| .80 |
|
6.0 |
|
10.34 |
|
14.5 |
|
|
|
|
|
|
|
| .85 |
|
6.2 |
|
12.00 |
|
15.0 |
|
|
|
|
|
|
|
| .95 |
|
6.4 |
|
12.92 |
|
15.4 |
|
|
|
|
|
|
|
| 1.00 |
|
6.5 |
|
13.17 |
|
15.5 |
|
|
|
|
|
|
|
| 1.10 |
|
6.6 |
|
14.50 |
|
16.0 |
|
|
|
|
|
|
|
| 1.17 |
|
6.8 |
|
|
|
|
|
|
|
|
|
|
|
Source: Gemological Institute of America (GIA) |
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Ring Size Table
To determine your ring size:
- Find a piece of string or strip of paper not wider than 3/4"
- Circle it around the base of the finger
- Mark the point where the two ends overlap and measure the length
- Refer to the following table to determine your ring size
| |
Ring Size (USA) |
Length (inches) |
Length (mm.) |
|
|
|
|
|
| |
4.0 |
1-13/16 |
46.5 |
|
|
|
|
|
| |
4.5 |
1-7/8 |
47.8 |
|
|
|
|
|
| |
5.0 |
1-15/16 |
49 |
|
|
|
|
|
| |
5.5 |
2 |
50.3 |
|
|
|
|
|
| |
6 |
2-1/16 |
51.5 |
|
|
|
|
|
| |
6.5 |
2-1/8 |
52.8 |
|
|
|
|
|
| |
7 |
2-3/16 |
54 |
|
|
|
|
|
| |
7.5 |
2-1/4 |
55.3 |
|
|
|
|
|
| |
8 |
2-5/16 |
56.6 |
|
|
|
|
|
| |
8.5 |
2-3/8 |
57.8 |
|
|
|
|
|
| |
9.0 |
2-7/16 |
59.1 |
|
|
|
|
|
| |
9.5 |
2-1/2 |
60.3 |
|
|
|
|
|
| |
10 |
2-9/16 |
61.6 |
|
|
|
|
|
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Diamond Care
Diamond is the hardest natural substance on Earth. It can cut any kind of rock or metal, but only another diamond can cut a diamond. In fact, a diamond must be heated to a temperature of 1292 degrees Fahrenheit before it will burn. However, the oil deposited from the mere touch of a human finger can cause dirt to collect and make this nearly indestructible gemstone quickly lose its sparkling appeal. The Gemological Institute of America (GIA) offers the following tips on diamond care:
-
Clean your diamond regularly. A simple plan to keep your diamond jewelry always looking beautiful is to soak the diamond in an ammonia-based household cleaner (such as window cleaner) overnight, once or twice weekly. In the morning, remove the diamond from the cleaner and brush it with a soft, clean toothbrush (one that has not previously been used in any way, and that you reserve exclusively for cleaning your diamond) to remove any leftover dirt. Take extra care to brush the back of the diamond as this will be the area that has collected the most oil and dirt.
Be aware that fragile settings and estate jewelry won’t take kindly to being scrubbed with a toothbrush, so use a soft touch. Then, just rinse the diamond with water and wipe with a soft, lint-free cloth.
-
Don’t use harmful solutions. Chlorine (as in household bleach) or abrasives (such as household cleansers or toothpaste) should never be used when cleaning diamonds, especially those set in jewelry. These erode some of the metals often used in diamond settings, and may loosen prongs, or even dissolve the metal completely.
-
Sometimes an ultrasonic cleaner is necessary to remove encrusted dirt on diamonds. By sending high frequency sound waves through a detergent solution, ultrasonic cleaners cause vibrating fluid to remove accumulated dirt and grime. However, they can also shake loose stones from their mounting, so this method shouldn’t be used on fragile settings (or estate jewelry), and is best undertaken by a professional jeweler.
Regular cleaning will keep your diamond jewelry in gleaming condition and ready to sparkle on that special occasion.
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Platinum versus White Gold
- Metal Density Comparing inch for inch, platinum is a heavier and denser metal than white gold. One can easily tell by the weight difference of the platinum.
- Color Platinum has a darker white color than white gold. Platinum looks rather grayish. Over long periods of time, platinum maintains its grayish white color whereas white gold may eventually tinge to a very light yellow as a result of being exposed to skin acids.
- Durability Platinum scratches easier than white gold.
- Sheen White gold maintains its sheen longer than platinum. After polishing, white gold will look shinier for a longer time than platinum.
- Wearability White gold wears thin over long periods of time. For example, a ring shank may have to be eventually replaced after fifty years. On the other hand, the shank on a platinum ring will remain as thick as it was on the day it was purchased.
- Price The price of platinum is 3 to 4 times higher than the price of white gold
- Maintenance Over time, occasional maintenance on platinum involves visits to the jeweler for re-polishing. Maintenance for white gold, however, can include re-polishing, rhodium finish re-plating, and/or eventual replacement of shanks.
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Millimeter (mm) to Inch (in) Converter Chart
Millimeter to Inch Converter Chart
1 inch [in] is equivalent to 25.40 millimeters [mm] |
mm |
Approx. inch |
| 1 mm |
1/32 in |
| 2 mm |
1/16 in |
| 3 mm |
3/32 in |
| 4 mm |
1/8 in |
| 5 mm |
3/16 in |
| 6 mm |
Just under 1/4 in |
| 7 mm |
Just over 1/4 in |
| 8 mm |
5/16 in |
| 9 mm |
Just under 3/8 in |
| 10 mm |
Just over 3/8 in |
| 11 mm |
7/16 in |
| 12 mm |
Just under 1/2 in |
| 13 mm |
Just over 1/2 in |
| 14 mm |
9/16 in |
| 15 mm |
Just under 5/8 in |
| 16 mm |
5/8 in |
| 17 mm |
Just under 11/16 in |
| 18 mm |
Just under 3/4 in |
| 19 mm |
Just over 3/4 in |
| 20 mm |
Just under 13/16 in |
| 21 mm |
Just over 13/16 in |
| 22 mm |
Just under 7/8 in |
| 23 mm |
Just over 7/8 in |
| 24 mm |
15/16 in |
| 25 mm |
1 in |
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Jewelry Stamping: Hallmarks
By law, jewelry items have to be marked with a metal purity hallmark and a trademark of the manufacturer/artist. Jewelry weighing below 2 grams does not require marking. Usually, hallmarks are found on the back side of the jewelry or near the clasps. Often, the marks are very small in size and require the use of a magnifying glass in order to observe their detail.
When a composition of metals is used in jewelry, the mark would correspond to the lowest value metal used. For example, 925 mark will appear on an item composed of both 14K Gold and Sterling Silver, 14K mark will appear on an item containing both 14K and 24K Gold, etc. The description of the item may, of course, include all types of metals and composites used for crafting the item.
Below is a list of hallmarks commonly used for marking jewelry:
24 Karat Gold - 24K or 999
22 Karat Gold - 22K or 917
21 Karat Gold - 21K or 875
18 Karat Gold - 18K or 750
14 Karat Gold - 14K or 585
14 Karat Goldfilled - 14K GF or 14K/20
10 Karat Gold - 10K or 417
9 Karat Gold - 9K or 375
Sterling Silver - 925
Pure Silver - 999
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Common Gemstome Cuts
Cabochon - Dome shape polished gemstone. One side of the stone is flat and the other is in dome shape. |
Round Amethyst cabochons |
Rose Cut - The stone is cut in way that its bottom is flat and the top is faceted. |
Round faceted Smoky Quartz gemstone |
Emerald cut / Octagon cut - Square or rectangle shaped stones with truncated corners. Facets run in steps parallel to the gemstone circumference. |
Left to right: Iolite, Emerald and Ruby, emerald-cut gemstones |
Faceted - Gemstone cut in a way to include many facets. The multiple facets structure increases light reflection and gives the stone a bright and shining look. |
Faceted oval Citrine gemstones
Faceted Crystal and Blue Goldstone beads |
Brilliant cut / Diamond cut - The most famous faceted cut used for round gemstones. The stone is cut with 58 facets in a special geometry for very high light reflection. The incident light enters the stone through the flat top surface, circulates within the stone and reflected back from the top surface. Commonly used for diamonds. |
Brilliant cut Blue Topaz and Iolite gemstones
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