Utah Rock Origins

Here's an excerpt from Jack's first email (in case I missed something in the above post):

Jon,  thanks for your message.  I have just returned from Utah where I was doing field work on Great Salt Lake and Lake Bonneville -- sorry to be slow to respond to your questions.

The photographs you attached to your message show that the material you have collected is tufa from Lake Bonneville.  Tufa is calcium carbonate that precipitated from the waters of Lake Bonneville and is very common in the basin.  In some places it is aragonitic and in other places it is calcitic (or both), and in places it cements shorezone gravel (the gravel you have called "river rock" is most likely beach gravel).  The tufa head you have pictured probably formed at the bottom of the lake when it was pretty shallow at this location (most likely during the transgressive phase of the lake sometime between 25 and 15,000 years ago, depending on the elevation), and probably was aided in its precipitation by the photosynthesis of algae (which removes CO2 from the water and raises the pH, this inducing CaCO3 precipitation).

 

Bonneville tufa deposits vary in composition and purity -- some are

very clean and pure aragonite or calcite, some are "dirty" in that they contain lots of sediment, sand or rock fragments, and some are highly weathered.  I don't know anything about fish tanks so I can't judge whether tufa would be appropriate, but I would guess that if it is clean tufa and not too weathered, that it might work well.  To determine whether the tufa is aragonite or calcite would probably require analysis by X-ray diffraction (a common procedure used by geologists).  Dr. Marjorie Chan in the Department of Geology and Geophysics at the U of U might be able to help you with other questions.

Travis wrote: So is the conclusion that it's fine for aquariums??

If it's not fine I think lots of people would have had a lot more problems.  Many of us have been using it for years.

The real discussion has been over how beneficial it is and how it compares to store bought Live rock.  Showing that it's aaragonite goes a long way IMHO to show that once properly seeded and aged it's just as good as normal live rock.

Thanks guys.  I've always had more then a passing interest in geology, so it's been fun.  And I almost posted this thread in the off-topic area 'cause I don't have any more info regarding it's aquarium use...

My crude density measurements suggest that it is aragonite, but I think x-ray diffraction is probably the only way to know for sure.  BUT, imo, it really doesn't matter.   And I'd be more comfortable using it in a reef tank if it were calcite anyway.  And Mark picked up on what this really means... there's tons of this stuff out there!  If you have a GPS you would want to concentrate in the 4400 ft elevation (Stansbury level) and 4740 ft elevation (Provo level).  And you want to find a spot where the lake would have been shallow, so the wasatch front mountains are probably not a good place, but sections of the west desert would be.

Should Utah rocks be replaced in our tanks once in a while?