Focus

A focus is a material object, crafted by a mage, as an external channel for his or her Talent and magical power. A focus is generally required for complex, difficult, and time-consuming magical work, such as protecting a house, crafting a magical object, scrying, information spells, and long-term enhancements or curses. Ritual magic also requires a focus.
Foci range in size, shape, and material, but most are small enough to be easily carried or worn. Common foci forms include:

• wands, staves, and rods (wooden or metal, sometimes glass)
• jewelry (necklaces, rings, bracelets, earrings, medallions, pins)
• eye wear (eyeglasses, monocles, sunglasses)
• crystals (quartz and similar)
• gemstones (precious or semi-precious)
• glass mirrors
• river or ocean stones
• talismans

Obviously, foci can be made of many different materials: wood, metal, precious metals, stones and gemstones. Even sea shells, leather, paper, bone, and glass can be used. Natural materials are preferred to synthetics, and mixed materials (as a wooden staff set with a crystal or a silver ring set with an amethyst) may be used. The object that serves as the focus may be made by a craftsman, but the mage must make the object into a focus. In other words, a mage need not be a jeweler to craft a ring-focus.
Most mages craft their first focus at age thirteen and wear or carry their foci continually after that time. (Some mages craft a second, larger focus for dedicated, stationary operations, such as alchemy or cooking or baking.) Because many mages interact with mundane people regularly, many prefer to craft a focus that can blend into the mundane world easily: charms, crystals, or talismans worn as necklaces, rings, watches, eyeglasses, or "lucky" or "worry" stones.

Significance

Foci generally reflect the personality of the mages who make them, and usually indicate the preferred magical style of mages. They can also reflect culture, religion, ethnicity, and background, through the materials chosen and the symbolism incorporated.

Rarity

Common. Most mages have a focus.
A mage may have more than one focus. Some develop different foci for different purposes. A mage who works alchemy, for instance, may have a quartz crystal as an everyday sort of focus, but may also make his or her favorite alchemical vessel into a focus as well.  
Some mages also develop different foci over the course of their lifetimes because of their changing circumstances.

Weight

Varies, according to object

Dimensions

Varies, according to object. Generally, they are small enough to be worn or carried in a pocket, but they can be larger as well.

Base Price

Varies according to material. Some foci are made of easily obtainable and cheap materials, such as wood or iron or quartz, while others are constructed of gold, silver, and gemstones.