The opinions expressed here are well-reasoned and insightful -- needless to say they are not the opinions of my employers

12 July 2010

In praise of green rocks

I've been following the hoopla/outrage over the California state legislature's latest intrusion into the byzantine world of state symbols for the past month, but have been reticent to dip my toes into the metaphorical waters -- I still feel bruised and abused over the battle between my beloved banana slug and the evil abalone for official state mollusk -- a battle that never so much ended as it dragged on into a stalemate, much like the Korean war (shut up, this is a great simile -- did you know that abalones are big supporters of Kim Jong Il?)...

Anyway, like Garry I have begun to compose a letter to the relevant assembly committees, members, and governators. I will print this out in multiple copies that will be sent out by snail mail, as my understanding is that no one pays more attention to your opinions than when you kill trees to express them (well, unless you give them lots of money).

For those who still read my rare ramblings, I'm interested in your input before I put this to bed. Some of the points have been made previously in this thread, though the only material I consciously cribbed was Chuck's points about talc formation and carbon sequestration:

Governor Schwarzenegger and Members of the Assembly and the Senate:

The California Legislature is currently considering a bill (Senate Bill 624) that would strip serpentine of its designation as the state rock of California, while declaring it to represent a hazard to the health of the state’s residents. I am writing to express my strong disagreement with this bill, and my dismay with some of the misguided or misleading arguments in support it. I am a graduate of both UC Berkeley and UC Santa Cruz, a professor of Geology at Saddleback College, and a member of the National Association of Geoscience Teachers, The Geological Society of America, and the American Geophysical Union, and while this letter represents my informed opinion as a scientist and educator, it does not necessarily represent the opinions of these institutions.

The rock serpentine (or serpentinite, the accepted geologic term for the rock) is commonly associated with the convergence of tectonic plates. It is formed from shallow mantle rocks (called “ultramafic” rocks) that have been altered by high-temperature fluids and then squeezed between two plates at (relatively) low temperatures. Outcrops of the rock are commonly pushed to the Earth’s surface along fault zones.

In California serpentinite is most common in the metamorphic belts of the Coast Ranges and in the Sierra Nevada foothills. The formation of serpentinite in our state is associated with the subduction of the Farallon Plate beneath the North American Plate beginning in the Mesozoic era and continuing until plate was completely consumed and the San Andreas Fault became active about 30 million years ago. Though it is found in many places in the world, the processes that brought it to the surface here have not occurred commonly so its abundance here is unique.

In the presence of water and CO2 serpentinite can produce the soft slippery mineral talc, the primary component of talcum powder. This reaction has been proposed as a hypothesis to explain why some major and minor faults or fault segments in California move gradually and do not produce large earthquakes. Its ability to absorb carbon dioxide makes serpentine one of the more promising geo-engineering sinks for this rising atmospheric gas.

The yellow-green to blue-green color commonly found in the serpentine minerals antigorite and lizardite, along with the polishing of the rock through movement along fault lines, produces beautiful exposures of jade-like rock in many areas. Serpentinite is a common decorative stone, used in countertops and tiles, and was a common choice, along with white marble, for columns and sculpture by Roman artists and architects.

The soils produced by the weathering of serpentinite lack certain elements (calcium, nitrogen, potassium, phosphorus) necessary for most plants, and are abundant in others (chrome, nickel, and selenium) that are poisonous to most plants. The process of evolution has led to unique plant communities found nowhere else but California. Trees such as the Jeffrey Pine and shrubs such as the Manzanita thrive on these soils. Because they have evolved to absorb heavy metals some of these plants have been used in the process of bioremediation.

The analysis of SB 624 “declares that serpentine contains the deadly mineral chrysotile asbestos and that exposure to it increases the risk of the cancer mesothelioma,” and “declares that California should not designate serpentine as the state rock due to its known toxic health effects.” Serpentinite is not a poisonous rock, at least not in the sense that exposure to natural outcrops of the rock represent a danger.

Rocks are agglomerations of several minerals, and though serpentinite is mostly made of antigorite and lizardite, chrysotile is another serpentine-group mineral that is sometimes present. Chrysotile is an “asbestiform” mineral, meaning that it grows crystals that are fibrous (i.e., thin and flexible). It shares this form and designation with several different minerals in the amphibole group, including amosite and crocidolite (neither of which is associated with serpentinite). Note here that the term “asbestos” refers not to a specific mineral or rock but to a particular crystal form that a few minerals take.

While the inhalation of any ground-up rock dust (i.e., silica or coal dust) is dangerous, because of their fibrous nature exposure to asbestos minerals can present significant health problems. Long-term exposure to asbestos minerals in the extraction or processing industries has been shown to represent a health hazard, the strongest correlations are associated with exposure to the amphibole group minerals; though most asbestos formerly used in construction was of the chrysotile variety, correlation between cancer and exposure specifically to chrysotile is not nearly as strong.

Let me emphasize here that I am not suggesting that asbestos exposure is not a health hazard nor am I suggesting that lung cancer and mesothelioma are not serious health problems that the state should concern itself with. These dangers to public health are established, and state law already deals with exposure to these materials.

My primary concern here is that this legislation expands that declaration to include not just industrial exposure to airborne chrysotile fibers but to casual exposure to unbroken bulk samples or outcrops of serpentinite itself (would I still be allowed to have hand samples of serpentinite in my classroom, or to pass them around to students in my lab?). It would be as if the state were to declare granite to be hazardous because it contains trace amounts of radioactive elements, or to eliminate the California Poppy as the official state flower (and to declare it represents a hazard) because it contains alkaloids related to opium and morphine.

Many citizens feel that the designation of an official state rock, mineral, flower, song, vertebrate or invertebrate fossil, etc., is a frivolous exercise with which state government should not concern itself. State Government has an important role, however, in promoting the appreciation of the state’s historical, cultural and natural attributes. For California educators our park system, our museums, and the acknowledgment of state symbols, whether it is the state rock, the state flower, the state motto, or the grizzly bear on the state flag (the state animal), provide a jumping-off point for the discussion of the geological, biological, and cultural wonderland in which we are privileged to live and work.


James L. Repka

Professor of Earth and Ocean Sciences


Garry Hayes said...

A most excellent letter. I hope assembly members are hearing more and more like this, and I hope it will make a difference. Something this whole episode just reeks.

Andrew Alden, Oakland Geology blog said...

Jut as you say, well-reasoned and insightful. You might underline, "This is what I teach my students"

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