Brass-an alloy of copper, zinc and sometimes other metals. The surfaces of raw brass items may be imperfect, and require polishing, and their finish may change with age. Anti-tarnish brass (a proprietary alloy) looks very close to the color of 14kt gold.
Copper-an elemental metal that is bright reddish-orange in color. It's a very reactive metal, meaning over time, it will darken and gain a patina, sometimes with a greenish hue. Copper can also discolor skin, most commonly when it is worn snugly like a finger ring or tight-fitting bracelet. Because of copper's softness, solid copper components may bend easier than copper-plated beads and findings.
Niobium-highly resistant to corrosion and other reactions. Niobium Jewelry findings come in several anodized colors. Anodizing is a way to color metal by dipping it into an electrically charged "bath" that creates bright colors without plating or painting the surface. Niobium is an inert element with no nickel, lead, or other additives, most people with metal allergies can safely wear niobium.
Stainless steel-The advantage of stainless steels over plated steels is that, if scratched or damaged, the stainless steel 'self-repairs' as a new chromium-oxide layer is formed.
Surgical stainless steel-a specific type of stainless steel which, while wearable by the majority of the population, does contain a small amount of nickel (to which some people are allergic).
The term precious metal refers to rare metals of high economic value. A metal can be considered a "noble" metal (meaning it is highly resistant to corrosion) without being a "precious" metal.
Sterling silver-an alloy of at least 92.5% silver, and (usually) copper. It can be antiqued to a dark black or polished to a bright shine.
Fine silver-at least 99.9% pure silver, which means it is softer and more malleable than sterling. It also tends to take longer to tarnish.
Silver fill-made by using heat and pressure to apply a layer of .925 sterling or .999 fine silver to a base of less costly metal. This produces a surface of sterling silver or fine silver that is hundreds of times thicker than a silver plating.
Gold fill-Seamless and double clad gold-filled items are less likely to discolor, since the base metal is sealed inside the gold. Use care when buffing gold-filled items, to avoid removing the gold layer.
White plate-the "silver" color most often seen on costume jewelry and base-metal findings. White-plated components are generally grayer, but also more durable, than silver-plated components. They generally do not tarnish. Some white-plated components have a plating of real rhodium over a nickel undercoating. There is potentional for the nickel undercoating to leach, making some rhodium-plated supplies not fully compliant with the EU Nickel Directive. Rhodium is brighter and more silvery than other white platings, but still more gray than actual silver.
Silver plate-a thin surface layer of actual silver. It nicely matches the color of sterling silver; it doesn't quite match white findings. Like sterling silver, silver plate can tarnish. For this reason, it's frequently lacquered to prevent or slow tarnish.
Yellow plate-a gold-colored plating that is slightly brassier than gold plate and is sometimes longer lasting. Yellow finishes go best with raw brass.
Gold plate-a very thin deposit of actual gold. Warning: hand lotion will accelerate tarnish on gold plated components and can result in a black color within days of handling.
Copper plate-a bright, shiny copper plating. Because the metal underneath the plating is usually a harder metal than copper, copper-plated components tend to be more durable than solid copper parts.
Gunmetal plating-varies in color from gun blue to matte dark gray to shiny black metal. It often consists of black nickel plated over brass, but some gunmetal components do meet the EU Nickel Directive.
Information borrowed with permission from the following Rings & Things website: