Apatite, Orthoclase & Quartz
Apatite is the name of a group of calcium phosphate minerals: fluorapatite, chlorapatite and hydroxylapatite. All have a similar chemical composition and prismatic hexagonal crystal shape, but varying amounts of fluorine, chlorine and hydroxyl. Hydroxylapatite is one of the main constituents of bone and tooth enamel. Outside of the biological world, fluorapatite is the most common, occurring in igneous, sedimentary and metamorphic rocks. Apatite contains clues like fission tracks that help geologists to understand the Earth’s history. Methods like apatite fission track dating tell us about the cooling history of a rock, helping us to understand how fast a mountain belt grew or was eroded, or when a magma body cooled. Apatite is most commonly used to produce fertilizers because it contains phosphate, an important element in plant growth. Sometime rare earth elements, important in modern electronics and magnets, substitute for calcium in apatite. If concentrations of rare earth elements are high enough, apatite can be considered an ore mineral, but only a few apatite rare earth element deposits have been discovered so far.
Orthoclase is a potassium-rich member of the feldspar group. Potassium feldspar, or K-feldpar, is a relatively common mineral, occurring in many types of igneous and sedimentary rocks. It is most commonly pink in colour, but can also be colourless, white or pale green, yellow or grey. It can be easily confused with more calcium- or sodium-rich feldspars. Orthoclase and sodium-rich feldspar (albite) can intergrow to form moonstone, which has a shimmering pale grey-white lustra and is used to make jewellery.
Quartz is the second most abundant mineral on Earth, occurring in many different types of rocks. Although usually clear or milky white in colour, quartz can be found in a variety of colours because of impurities in the crystal structure. Pure quartz is made up of silicon and oxygen only, but atoms of other elements, like iron or titanium, often make their way into the quartz crystal structure. Some varieties of quartz, like purple amethyst, are considered to be semi-precious gemstones and have been used since ancient times to make jewellery and decorative objects.
This sample is from the Blue River area east of Wells Grey Provincial Park in central BC. It contains white orthoclase with well-formed crystals and clear quartz and apatite. Small dark flakes of mica can also be seen.
Store: Association for Mineral Exploration (AME)
Accession #: AME 446
Primary Mineral: Apatite, Orthoclase
Secondary Mineral: Quartz
Site Locality: –
Location: Blue River, British Columbia
Special Features: n/a