Bill Long 10/31/04
Now that my screed is over, we can get down to work. Apatite, according to the OED, is
"a native crystallized phosphate of lime, varying in color from white to green, blue, violet, brown; transparent, translucent, opaque."
The word only takes up about 1/6 of one column of one page of the OED, and there is no family of English words connected with it. Like the biblical Melchizedek (according to the Book of Hebrews), it appears to be "without mother or father" (i.e., no related terms) though we know it is derived from the Greek word for "deception." It is rarely used as a gemstone, but frequently used in fertilizer.
Even the more verbose Century Dictionary and Cyclopedia of 1911 defines it sparsely:
"Native calcium phosphate with calcium fluorid or chlorid, generally crystallized in hexagonal prisms, which are sometimes low or even tabular, sometimes elongated, and occasionally of great size."
We need to go further.
The name was given it in 1786 by the father of mineralogy, Abraham Gottlob Werner (1749-1817). Werner was the Linneaus of mineralogy, and strove to develop a system through which minerals could be classified. His seven-fold system of classifying for color, crystal form, crystal habit, cleavage, luster, streak and hardness survives today, supplemented by other categories that make determinations more precise. For example, the Mohs scale, developed by German mineraologist Frederick Mohs in 1812 put a number on each mineral, based on its hardness. Apatite is a "5" on the hardness scale.
Werner called it apatite because of its "deceptive" similarity to more valuable minerals such as olivine, periodot and beryl. As indicated in the OED defintion, it could be white or blue or green or violet or brown. We have specimens today that are pink or even yellow. It can appear in igneous, metamorphic or sedimentary rock. In addition, the OED says it can be opaque, transparent or translucent. You realize that you have just about covered all the bases.
But we can be more precise about apatite, despite its tendency to deceive us. It has a hexagonal crystal structure, which means that "a simple six-sided prism is terminated at each end by the two faces of a basal pinacoid."* Ok. We also know that numerous
[*Glad that you asked what "pinacoid" means. It means, with respect to crystals, a plane that is parallel to two planes of a cubic figure and intersects the third.]
substitutions can occur in the chemical structure of apatite (at this point it wouldn't help if I was just to give all kinds of chemical symbols). For example, calcium may be replaced by strontium, manganese, or even the rare-earth elements of cerium, lanthanum or yttrium. Apatite is actually three different minerals, based on the predominance of fluorite (Fluorapatite), chlorine (Chlorapatite), or hydroxyl (Hydroxylapatite) in a particular sample.
Apatite is a phosphate. There are 10 categories of minerals, and I might as well list them here. All minerals (a mineral is something inorganic) are either elements, oxides, halides, carbonates, sulfides, phosphates, sulfates, silicates, organics or mineraloids. Ninety percent of gems are silicates, but not apatite.
Apatite and the Cycle of Life
I mentioned in the previous essay that apatite or an apatite-like mineral is more present in us than any other mineral. Apatite is also the principal source of the element phosphorus, an essential component of every living cell, plant and animal. According to Court and Campbell (Minerals: Nature's Fabulous Jewesls), virtually all the world's phosphorus is locked up in apatite. Whenever any rock in which which apatite appears weathers or decomposes, it releases some phosphorus, which finds its way into ground-water, streams and soils. Plants absorb phosphorus through the soil; herbivores eat the plants, and phosphorous enters into their cells. Some of the phosphorus released from the rocks also seeps into the sea and is consumed by fish. They are eaten by birds, which excrete the phosphorus and in some cases in such quantities that islands developed. These islands, called "guano islands" (after the bird-droppings) were even the subject of federal legislation in 1856. The "Guano Islands Act" was passed in that year by Congress, thus enabling citizens of the US. to take possession of islands containing guano deposits. This rich fertilizer, then, helped spur the development of American agriculture after the Civil War.
Much more could be said about apatite. Suffice it to say that yellow apatite is the most common, found primarily in Mexico and on the Iranian Island of Hormuz, in the straits of the same name. Various colors of apatite have been found in Spain, Portugal, Myanmar, Sri Lanka, Brazil and many American states. If I were apatite, I would object to my name. Rather than being deceptive, I would argue that I am life-giving. Maybe I would argue for my name to be "biophorous" or something like that. But, then again, apatite is mute, and has very few supporters in Congress.
Copyright © 2004-2010 William R. Long