It can seem risky to purchase something as valuable as a diamond online, so do your research: Does the company fully insure the diamond when it is shipped? Does the company have good reviews by customers? Are you protected by a robust return policy in case you do not like the diamond?
What Should I Look For?

Get familiar with the characteristics of loose diamonds:
Diamond Shape: If you are purchasing a diamond to place in a setting, consider the shape that would look best in the setting and conform to the wearer’s style. If you are purchasing as an investment, think about classic shapes that never go out of style.
Diamond Color: Diamonds are either “white” or “fancy color”. White diamond color is graded on a lettered scale from D (perfectly colorless) to Z (light yellow), with the highest value placed on the least colored stones. Fancy color stones are graded based on intensity, with the more intense color being of a higher value.
Diamond Clarity: Clarity refers to any flaws in or on the diamond. “FL” clarity means flawless, while other ratings describe a progressively more flawed stone: IF, VVS1, VVS2, VS1, VS2, SI1, SI2, SI3, I1. This is an important factor when determining your budget for a loose diamond.
Diamond Cut: The best-cut diamonds are excellent at reflecting light, which is the appeal of a diamond in the first place. In order from best to worst, here are the grades: Super Ideal, Ideal, Excellent, Very Good, and Good.
Diamond Carat weight: Carat is a unit of measure that is used to refer to the weight of a gemstone. Carat weight is a used as a rough estimation of size when discussing diamonds.
Diamond Certification: This is the most important step in purchasing a loose diamond, online or in person. To be certified, a diamond must be inspected by a licensed gemologist in a laboratory setting. The certificate verifies each of the characteristics listed above for that particular diamond. Purchasing a certified diamond is extremely important if you are planning to use the diamond as an investment because the certificate serves as an independent and objective summary of the diamond’s quality, verifying its value.