I took the kids to a local construction site today after we were told they were pulling up some cool looking crystals. Well we found some pretty neat ones in diamond and rod shapes. We began noticing that they were in the piles where clay had been pulled up so we focused on the clay and that helped a lot. We also noticed that these were not quartz – they had a different look to them. All of the crystals we found were clear – some had dirt embedded in the middle as though the crystals had formed around it.

So after some basic web research we have learned that what we found was gypsum. Apparently there is quite a lot of it in Southern Manitoba because there is a serious clay layer left behind after the glacial Lake Agassiz dried up after the Ice Age about 10,000 years ago. The gypsum could have formed about 13,000 years ago when Lake Agassiz existed. This is not standard gypsum but a less common kind called Selinite. There’s a ton of it around here (at least at the dig we were at).

We got pretty muddy but all of the kids found crystals. I have added some pictures here.

The coolest thing is that one of the crystals very clearly has an insect embedded in it. Looking closely at it I think it is a mosquito larva which is appropriate for Manitoba. If the selenite was formed in the Lake Agassiz era than we could have a 10,000-year-old mosquito larva in our house. Very cool. Maybe we could extract the DNA, clone it and return ice age mosquitos to the province. Hmmmm?

MORE INFO: After a while people begin to realize that I get a little intense into subjects when they have me in their grasp. I am a research-oriented person and these little rocks have grabbed hold for the time being. I have been reading the geological history of Lake Agassiz and the area.

The latest info I have been reading comes compliments of the State of North Dakota Geological Survey (NDGS). When we were hunting this afternoon one of the ways we were able to find the clay quickly was that it was laced with an odd-yellow dirt…very different from the typical soil. The NDGS mentions the formation of this kind of clay on their website:

The exposures of shale are interrupted in places by thin beds of yellowish-colored bentonitic clays.   These bentonites are weathered volcanic ash beds.   Clouds of ash, from volcanoes erupting in the developing Rocky Mountains, far to the west in Wyoming and Montana, blew eastward over North Dakota, settling in the shallow sea that covered the area.

It’s kind of cool to know we were looking at ash from west-coast volcanoes during the infancy of the Rockies.