Notes

Article About Gemstones
Article about Gemstone

A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli) and organic materials (such as amber or jet) are not minerals, but are still used for jewelry and other decorative purposes. The word "gem" derives from the Latin gemma, meaning "budding",[1] which itself was derived from the Greek word γέμμα[2][3] ("gemma") with the same meaning.[citation needed]

Until recently,[when?] all gems were graded using objective criteria based on their physical properties such as color, clarity, weight, and hardness. Over time,[when?] however, it has become apparent that these factors say little about a gem's true beauty and value. For example, two diamonds may have identical objective properties yet look quite different to the naked eye because of subtle variations in their atomic structure; these differences result in what gemologists call optical phenomena such as fire or dispersion. As a result of this shift in emphasis from quantitative to qualitative grading systems,[which?] many new terms have been added to the lexicon of Gemology.

Fire: The play of spectral colors visible within a stone when it is viewed face-up in incident light (as opposed to transmitted light). Also known as dispersion.
Luster: The way light reflects off the surface of a stone. Common luster types include adamantine (brilliant), vitreous (glassy), silky, pearly, and greasy.
Transparency: The degree to which light can pass through a stone; also known as diaphaneity. Transparent stones are considered more valuable than opaque ones.
Cut: https://www.zogby.com/gemstones/ in which a stone has been faceted (or cut). This can greatly affect a stone's appearance as well as its value.
Clarity: A measure of the number and size of inclusions (internal flaws) or blemishes (external flaws) present in a stone. A completely flawless stone is considered "flawless" while one with significant inclusions is "included".
Color: Probably the most important factor in determining a gem's value, color refers to the hue, saturation, and tone of a stone. Hue is the basic color; for example, red, blue, or yellow. Saturation refers to the intensity of that hue, while tone refers to how light or dark it appears.
Carat weight: The standard unit of measurement for diamonds and other gems; one carat equals 0.2 grams. Carat weight alone does not determine value; two stones of equal carat weight may have very different values depending on their other qualities.
Hardness: A measure of a gem's resistance to scratching, rubbing, or breaking. The hardest known substance is diamond, which has a hardness of 10 on the Mohs scale; talc, at the other end of the spectrum, has a hardness of just 1.

In recent years,[when?] there has been an increased focus on provenance (the history and source of a stone) as well as ethical considerations such as whether or not a stone has been treated or enhanced in some way. These factors are difficult to quantify but can greatly affect a gem's value.
My Website: https://www.zogby.com/gemstones/