Earth Blog

This afternoon, an article in the current issue of the magazine Elements – published by an international consortium of scientific societies for its members – drew my attention. The article that caught my eye is by Patricia Dove, on the development of skeletal biomineralization in the history of life on earth.

I first read about biomineralization some fifteen years ago, when I was working in the States. What I read, about the alternating growth of layers of oriented minerals and layers of organic matrix,  was entirely new to me, and I found it fascinating.

The research group I was part of at the time even had a little hobbyhorse in the area of biomineralization, to do with the strontium phosphate celestite, produced and rendered stable by small marine organisms called acantharians. These organisms made the impossible possible. That’s like magic!

So let me offer you a little appetizer extracted from and inspired by Patricia Dove’s article, in case you are not familiar with the topic of biomineralization yet.

By the start of the Phanerozoic – about 542 million years ago – many types of organisms had acquired this capability of influencing the time, location and morphology or mineral growth as part of tissue formation.

Skeleton formation is probably the best-known form of biomineralization. However, besides structural support, biominerals can also serve functions like filtration, grinding and cutting, light harvesting (part of photoreceptor systems), and magnetic guidance.

Most skeletal biominerals are carbonates, but there are also skeletons that rely on phosphates or silica. To date, more than 64 biomineral phases have been identified, including oxides, hydroxides, and metal sulfides. They are always, as it’s so nicely put, intimately associated with organic macromolecules such as proteins and polysaccharides.

Some organisms grow alternating layers of oriented minerals and organic matrix, and they do this with good reason. Targeted incorporation of 1 to 5 wt% of organic matter to create a composite with the carbonate mineral aragonite, for example, (pictured above as needles of a few millimeters in a German lava) can result in a local fracture toughness that is 1000 times higher than that of pure aragonite.

Bones are an example of the use of phosphate in skeletons; they consist of a composite of phosphate and collagen. The phosphate mineral in bones is apatite, shown below as an abiogenic mineral (and with thorium partly substituting for calcium as the sample is from La Celia in southeast Spain, from a lamproitic lava flow; the crystal size is about 1 cm):

Topics in the coming issues of Elements are the following:

• Sulfur – April 2010 (Vol. 6, No. 2) – including one article about sulfur on Mars;
• Metamorphism and the role of fluids – June 2010 (Vol. 6. No. 3) – including one article on metamorphic fluids and global environmental changes;
• Atmospheric particles – August 2010 (Vol. 6, No. 4) – including an article airborne particles in the urban environment;
• Thermodynamics of earth systems – October 2010 (Vol. 6, no. 5) – including an article on the effects of ocean acidification as a result of CO₂ dissolution;
• Sustainable remediation of soils – December 2010 (Vol. 6, no. 6) – including an article on assisted phytoremediation and one on the use of nanoparticles for remediation.

If you are interested but currently don’t receive the magazine, consider a membership in one or more of the following societies, of which it is a joint publication:

the Mineralogical Society of America, the Mineralogical Society of Great Britain and Ireland, the Geochemical Society, the Mineralogical Association of Canada, The Clay Minerals Society, the International Association of GeoChemistry, the European Association for Geochemistry, the Société Française de Minéralogie et de Cristallographie, the Association of Applied Geochemists, the Deutsche Mineralogische Gesellschaft, the International Association of Geoanalysts, the Società Italiana di Mineralogia e Petrologia, the Polskie Towarzystwo Mineralogiczne (Mineralogical Society of Poland), the Sociedad Española de Mineralogía (Spanish Mineralogical Society), or the Swiss Society of Mineralogy and Petrology).