Dark Moon: So Black, It’s Green.

June 15, 2007

 Nostoc cyanobacteria colonymantle minerals under the microscope

Tonight the scrying pool of the Dark Moon is more than a black mirror.  Now the Sun is strong enough to illuminate its shadowy green depths, since this moon will reflect the Summer Solstice light.  At the edge of the pool are tiny bubblelike jelly spheres of Nostoc, the same cyanobacteria (blue-green algae) that color the water.  They are some of the Old Ones, the first life on earth, who still live as though they are floating in the sea, for they brought Ocean with them when they first colonized rock faces, barren pools, and dry dust.  How?  Because the cell colonies, which look like strings of beads, are surrounded by a protective layer of clear jelly that traps water and binds soil and rock.  The Old Ones even make rocks of their own, and it as stromatolite fossils that we know their ancestors as the familiar string of spheres under the microscope.  The spherical shape and the alignment together spell LIFE in the most ancient fossils and in the modern nannobacteria that create rust and desert varnish.  The string of beads is Life’s earliest signature. 

Nostoc forms spherical jelly colonies in the desert soil. Each colony is only a millimeter in diameter, but together they form a black surface crust that fixes nitrogen, absorbs water, and keeps the soil from blowing away.  Their transparent blackish green (from magnesium in chlorophyll) is the same color as the iron-magnesium silicate minerals of the earth’s mantle.  These minerals – olivine, pyroxenes, spinel, and others – usually look black except when the microscope reveals their green radiance.  The first time I saw this, I felt that a window had opened into the deep earth, and the dark mantle-derived stones – peridotite, diamond-bearing kimberlite, serpentine, jade, and many more obscure rock types – have always been my favorites.  They have no connection with Life except color, and they are rare in the earth’s crust, so we forget that they make up most of the planet.  Below them, deep beyond the magnesium and silica, is the swirling magnetic iron of the earth’s metal core.  Like the earth, my heart holds iron, but it is locked in hemoglobin – a molecule very similar to chlorophyll, except that iron takes the place of magnesium – and the oxidized iron gives blood the same color as red ochre, which forms when the dark green mantle minerals oxidize or “rust” at the earth’s surface…often with the help of tiny bacteria.  To smelt iron, the red, brown, and yellow “rust” rocks go into the furnace, where they burn to yield a “bloom” of metal within a mantle of dark green glass, or silica slag.  When the liquid slag pours on the ground, it shatters as it cools into a rain of translucent blackish-green beads.  

The painting of a single Nostoc colony was done entirely with “biogenic” mineral pigments:  glauconite, the green clay that forms from marine worm castings in shallow water mud; charred bone black; blue vivianite that forms when these iron oxides meet phosphatic bone or shell.

The thin-section (transparent slice of rock made for viewing under a petrographic microscope) is a metamorphic rock with several mantle-derived Fe-Mg minerals, including bright green spinel and light green amphibole.


3 Responses to “Dark Moon: So Black, It’s Green.”

  1. Hemera said

    Beautiful artwork! I remember Nostoc from books..
    Do you do thin-sections from rocks and minerals yourself at home (in a home-lab) or is is done just in *big* labs? Thin-sections are easier from biological material but cutting minerals surely needs some pretty powerful tools?

  2. ironwing said

    I made some thin-sections when I was in school, but usually I’ve had them made. Most are done in small labs – all you need is a lapidary saw, epoxy, and grinding equipment (which can be a fancy thin-section machine that does a bunch at once, or one person with a glass plate and some jars of grit!). They’re easier to make than biological slides and don’t require as many special skills and tools.

  3. Karin said

    It’s a black, black Winter Solstice Moon here in Southern Gaia, and it rained for 2 days before today, when the sun rose so bright and clean to turn the water held in mossy roofs and walls into steam.

    A big black cat licked her kitten amidst the steam in a neighboring roof this morning.

    I remember the black Winter nights and days of endless rain in another city when I was a child. How I loved them. The world seemed to be torn apart. I guess that those were Black Moon nights, too.

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