I had a 64 dart that had similar stuff in the fuel tank. It was about 3/4 inch thick in the bottom of the tank {yeah I cut the tank in half with a sawzall. It seemed heavy even though I had drained the gas out/rinsed with water} Is it possible that this sediment could be lead from the gas that was used in the sixties? Maybe dirt from driving down country roads?
Never did figure that one out. I am serioud when I say it was at least 3/4 inch thick!! Maybe the filtering systems at the stations back in the sixties were not that good? The car was from montana originally and the sediment kinda looked like the dirt on the roads in montana. Very hard too. The car would run for about a mile and then just stop running. Let it sit for a couple of minutes and it would start back up so I figured it was the tank. Never did fix the car, ended up parting it out. The carb seemed to work ok when it did run though. Oh well, just my .02.....enjoy!

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

I used to live on the northern plains. The dust seems much finer than farther south. So much so that during the occasional dust storms it would remain suspended in the air like smoke and seep through cracks you couldn't even find in your house.

Also even though it was microscopic it was angular like the ground sand that was less fine. Poor folks would often build a house and dig a basement out under it later. In many areas the sand has no rock content and is extremely easy to dig when damp. These basements would be dug bigger and bigger over years to within a couple feet of the original foundation - with no concrete blocks holding it up. The angular sand in the walls locks together and when dry it gets almost as hard as half strength concrete. It will stand for decades that way and people take their time putting in concrete block walls.

I suppose all this is why pioneers often made homes called dugouts.