Apatite has several uses. Its most common function stems from high phosphorus content: the creation of fertilizer. It can also fluoridate water and provide protection against rust. Apatite also has the ability to screen radiation. According to the Washington State Department of Ecology, apatite chemically attracts strontium-90, a radioactive isotope that can pose long-term health risks.
Hardness
On the Mohs scale of mineral hardness, apatite ranks at 5, according to Geology.com. Talc ranks at 1, and diamond at 10. Apatite has the ability to scratch glass, but a steel knife can scratch it.
Luster
Luster refers to the way light interacts with the surface of a crystal. Apatite's luster can range from vitreous to subresinous. Vitreous luster resembles glass, meaning it has a high transparency. Resinous or subresinous luster, on the other hand, gives the crystal a more translucent appearance, similar to honey.
Cleavage and Crystal Structure
The cleavage of a mineral determines how smoothly fractures occur. Apatite has a poor cleavage--its fracture edges feel rough to the touch because it lacks planes of weakness. Apatite has a hexagonal crystalline structure. Therefore, individual pieces of apatite will naturally occur in a roughly hexagonal shape.
Streak
The streak of a mineral refers to the color of powdered residue it leaves behind when rubbed against a non-glazed ceramic surface. According to the San Diego Natural History Museum, the streak of a mineral never changes even if it has impurities. Apatite leaves a white streak.
Chemical Composition
The chemical composition of a mineral determines its crystalline structure. Geology.com states that apatite belongs to the calcium phosphate group. Some of the other elements that compose it include fluorine, chlorine and carbon. All forms of apatite have molecular structures of five calcium atoms bonded to three groups each of one phosphorus atom and four oxygen atoms.
Tags: crystalline structure, mineral determines, streak mineral
