Oolitic Sand Analysis

Background:
For those who are new, there is a naturally occuring oolitic sand found near the Great Salt Lake out on Stansbury Island.  Some hobbiest here have used this sand in their tanks.  Some hobbiest argue against the use of this sand for various reasons.  The purpose of this "experiement" was to test the GSL sand against some of the more popular oolitic sands, namely the Caribsea product and the Southdown play sand found in Home Depots back east.  Thanks to Mark Peterson for providing both the GSL oolitic and Caribsea oolitic.  Thanks to PC Pondbuilder for providing the Southdown.  The Southdown sand sampled was actually an OldCastle brand.  PC Pondbuilder has stated that OldCastle is the supplier to Southdown.

Executive Summary (for Adam... he's not reading the rest, not sure he even got this far ):
The results of these tests will probably not change many minds regarding the use/nonuse of the GSL sand.  The Caribsea and OldCastle sands test to be essentually the same.  It appears that Caribsea adds small shells and bits of shells to their oolitic sand.  The GSL sand tested 4.5 times higher in phosphorous then the other two.  There is also significantly more silica in the GSL sand.

Procedure:
20 grams of each sand was dissolved in 100 ml of 4 N HCl then diluted to 500 ml.  The samples were filtered and the filtered material weighed to determine how much silica sand was present.  Although this undisolved material was not analyzed, it was assumed to be silica.  It could also contain aluminum and other "clay" type constiguents.  For the purposes of this test anything that did not dissolve in HCl was considered "silica".  The dissolved sand sample was then titrated to determine calcium and magnesium content.  The magnesium number is really the total hardness due to compounds other the calcium.  Since strontium, iron, ect are most likely very low, the whole amount was assumed to be magnesium.  The pH of the dissolved sand sample was then increased to 4.0 by addition of 1 N NaOH.  This adjusted sample was then tested for iron, copper and phosphorous using a HACH 2000 Spectrophotometer.

Physical Appearance:
Since how a sand looks is important to most people, a picture of each of the sands is included.  The scale in all pictures is in mm.

Caribsea oolitic.

OldCastle oolitic.

GSL oolitic.

All three sands together to show the color differences.
Caribsea on left, Oldcastle in middle, GSL on right.

Here is a picture of the filtered "silica" sand that did not dissolve (sorry for the terrible pic).

One last picture.  The GSL sand that Mark supplied was washed but not screened.  About a year ago, I went out to the orginal dune and got some sand.  I washed and screened this sand.  The result is a sand closer is size to the Oldcastle.

Results:
The results of my testing is summarized in the following table.

The CaribSea and OldCastle oolitics tested identical in all aspects.  The GSL oolitic tested 4.5 times higher in phosphorous, 4 times higher in iron, 2 times higher in magnesium, 6 times higher in silica, the same in copper and slightly lower calcium when compared to the other two sands.  Whether this is significant or not is open to your debate.  There are many other elements that could be present that were not examined, I leave that exersise to someone else.

Thanks Jon.

Good information.

One thing I forgot to mention with regard to the sands.  The GSL sand dissolved as I expected.  Lots of bubbles but no foam.  Both the Caribsea and OldCastle sands dissolved and formed a very very stiff foam in the container (think Guiness on steroids).  It took hours for the foam to fall.  I wonder if both sands have an anti-caking agent added when they are bagged?  I was with Mark when he opened the bag of Caribsea and there was, to my nose, a slight fragrant smell unlike sand which did go away after a while.  Or maybe it foamed for some other reason??

Adam, yes I did the analysis myself and what kind of article?

Carl, I can't really answer those questions.  The P is significantly higher but I don't know if it's significant in the tank.  160 ppm is still a very small amount.  And it's most likely there as CaPO4 which is like 10,000 times more insoluble then CaCO3 which means it's that much less likely to dissolve.

This post is only to let everyone know that I have read the above but I will refrain from responding to the arguments.

Those go to Jon.  Thanks!  Too bad RIck Greenfield never got them done, but I trust the source now.

In this hobby maybe more than any other we are all trying new things, and part of this club is sharing the results of our varying success and allowing others to benefit from this information and decide for themselves if they want to try the same. In the instance of our local resources I believe the cost benefits and environmental conservation are worth considering. That's all I've got too say about that.

However, I'm shifting quickly to the aragocrete camp since I think I've conquered the pourousity issue, Just to incite the flames here are there any other drawbacks to aragocrete that anyone can point out to me? aside from cure time, I don't mind that, all things in this hobby take patience.