Quick and Easy Buying Guide
Carat weight: 1 carat = 200 milligrams = 6.5 mm diameter. Doubling weight doesn't double diameter.
Diamond clarity: FL/IF/VVS/VS = super expensive, near perfect. SI = best value if you can check a photo for obvious inclusions (defects).
Color: D-G = colorless, expensive, only if you have money to burn. H-J = best value. Can go lower in gold metal settings than white metal.
Cut: Better cut ratings let more light into a diamond, making it sparkle more. Very important property, don't skimp here.
Set a budget and minimum cut (Premium). Go J color for gold and I/H for white metals. Go searching for SI1/SI2 clarity diamonds at James Allen. Pick a diamond with small/no inclusions. Choose a ring setting and buy it risk-free (60-day returns).
0.85 Carat Diamond Sizes on Hand
This article gives an illustrated example of the actual size of a 0.85 carat diamond on an average woman's hand. Try to use the 6.2 mm average width of a 0.85 carat stone by measuring the size of your own finger in order to get an appreciation of what a diamond of this size will look like on your finger. A person's fingers could be quite a bit thicker or thinner than the ones of the woman in the image, which are quite thin - be sure to keep this in mind when you're looking at the picture. Try and avoid making the mistake I made of examing a potential diamond engagement ring placed on my own, large male finger - remember that it is ending up on a usually smaller and more delicate female hand, which will make the diamond appear significantly larger.