Blue Apatite

Blue apatite is the blue variety of apatite, a group of calcium phosphate minerals that share the formula Ca5(PO4)3(F,Cl,OH). Its color ranges from soft blue to intense neon blue-green, often colored by trace elements and sometimes enhanced.

Apatite is geologically and biologically important: it is the main phosphate mineral in rocks and the principal mineral component of bones and teeth in vertebrates. The name comes from a Greek word meaning "to deceive," because apatite is easily confused with other minerals.

With a hardness of only 5, apatite is relatively soft for a gemstone and is more popular among collectors than in everyday jewelry. It is the index mineral for hardness 5 on the Mohs scale.

Apatite forms in a wide variety of settings. It is a common accessory mineral in igneous rocks such as granite and pegmatite, and in carbonatites, where well-formed gem crystals can grow. It also occurs in metamorphic rocks and in hydrothermal veins.

Large sedimentary phosphate deposits (phosphorite) form on the seafloor from the accumulation of phosphate-rich organic material and are mined extensively for fertilizer, though these are usually fine-grained rather than gem material.

Gem-quality blue apatite comes from localities including Madagascar, Brazil, Myanmar, Mexico, and Morocco, with vivid neon blue-green stones associated with Madagascar.

Look for a blue to blue-green transparent-to-translucent stone with a vitreous luster and hardness 5, which means it is scratched by quartz and a steel file. Apatite often shows distinct dichroism (blue and yellowish or colorless) and may form hexagonal prismatic crystals.

It has a poor cleavage and brittle, conchoidal to uneven fracture, and a white streak. Many blue apatites fluoresce under UV light.

Look-alikes include paraiba tourmaline, blue topaz, aquamarine and blue zircon, all harder than apatite. The relatively low hardness (5) is the key clue: apatite scratches far more easily than tourmaline, topaz or beryl, so a hardness test readily separates them.

Gem apatite is faceted for collectors and cut into beads and cabochons, valued for vivid color, though its softness (5) and brittleness make it better for pendants and earrings than rings. Neon blue-green Madagascar apatite is especially sought after.

By far the most important use of apatite is industrial: phosphate rock is the world's primary source of phosphorus for fertilizers, and it is also used in phosphoric acid, animal feed and some phosphors. Synthetic apatite is used in dental and bone materials.

Metaphysically, blue apatite is associated with motivation, clarity and the throat, though these claims are not scientific.