Sapphires are a variety of gemstone, most commonly recognised as a deep blue gem (though in fact in comes in a variety of shades and colours). Valued not just for their beauty sapphires, are used as reagents in some vision magics (such as scrying the layout of nearby but hidden areas). The magical practitioner would use the sapphire as a focus as their senses would psychically reach outward. By the time the spell or ritual was completed the sapphire would crumble to dust.
The use of sapphires as reagents has declined in some parts of the demographic, such as mercenary groups. This is due to the development of scrying magics which do not need reagents to work. Although sapphires still find use in more esoteric areas.