Igneous Rocks

On our Igneous Rocks day, we did this igneous fudge activity. It was fun to make fudge, and it tasted good, but we found it really hard to tell the difference between the "intrusive" and the "extrusive" kinds. You could kind of detect a larger crystal size in the pan that cooled in the refrigerator, but it wasn't obvious. If I were doing it again, I would have instead re-done this igneous sugar activity that we did during our volcano unit. The results are much more stunning!  Of course, I think I also need a new candy thermometer (mine is about 30 degrees off, as far as I can tell, which doesn't make fudge-making easy).

We examined the igneous rocks from our rock collection.

We enjoyed this video on how granite is made into countertops.

We are lucky to have easily accessible examples of all three kinds of rocks in our nearby canyons, so using this guide, we spent a day driving around and looking at these examples. The igneous rock we saw was Quartz Monzonite in Little Cottonwood Canyon, which we have always known as "temple granite." Apparently, though it looks a lot like granite and the pioneers who built the Salt Lake Temple called it granite, it is not a TRUE granite. That's because true granite has over 20% quartz, while this rock at the Temple Quarry only contains about 5-20% quartz.


Little Cottonwood Canyon is a great example of a U-shaped valley, which means it was formed by a glacier.

There's an interesting little nature trail by the quarry, with signs that tell about some of the history of the area. Very beautiful.

Such a lovely Fall day!

Down in this rocky bed, it's fun to climb around and see the huge boulders of quartz monzonite!

As you can see, it has a lovely white-and-black-speckled appearance. It does look like granite. I don't know if you could tell them apart by just looking. You can tell it's an intrusive igneous rock, though,  because the mineral crystals are so large. The polished sheets of this rock that are on the outside of the Temple and the Conference Center are so pretty---the crystals gleam in the sun!

Basically this entire mountain is made up of quartz monzonite! It must have been a huge intrusion of magma which then was exposed through weathering and erosion.

Calcite Mine Field Trip

When I was in third grade, I went on a school field trip to "the calcite mine." It was somewhere out on the west side of Utah Lake, in the middle of nowhere it seemed to me, and I think it was on that same trip that we visited a Ghost Town (which I also don't remember the name of, or why it existed). I can't believe how much I've forgotten, but I DO remember the thrill of finding the beautiful pieces of calcite as they sparkled in the sun, and I remember collecting and taking home a whole bucketful (which my mom says she still has somewhere).

When we started this rock and mineral unit, my first thought was "maybe we can go to the calcite mine!" But I had no idea how to find it. I tried searching online but didn't find anything definitive, and that area has changed so much in the last 25 years, I wasn't even sure if the place still existed. I asked my mom and she had the same sort of vague memories of the place that I did---"somewhere west of Utah Lake."

Finally I found a blog post by someone talking about collecting calcite out near Pelican Point. That fit with what I remembered, so we decided to head down there and see what we could find. You drive way down Redwood Road until you get to Pelican Point, and then turn immediately west, toward the mountain, at the Dyno-Nobel sign. There are some areas fenced off that must be part of that, but as you drive west you soon pass some large piles of rock (mine tailings?) and some abandoned buildings that I'm guessing used to be part of a mining operation there. I have no idea if this is the same mine I visited in 3rd grade, but it had lots of beautiful calcite to pick up, and we loved it! 

I loved seeing the old buildings. To the right of this picture you can see the entrance to the mine (fenced off now). We peered in but couldn't see much.

Love this old boxcar too. And the advertising: "Be specific---ship Union Pacific!" Catchy!

Rickety conveyor belt

I love the banded pieces of calcite---such pretty colors and interesting patterns!

Sparkly!

Honey-colored calcite crystals

I love the neat way calcite cleaves apart---it makes such pretty little flat crystals!

Bands of calcite through rock

These crystals with flat faces are my very favorites

but Sam loves the tall, pointy ones best!

Those piles behind Seb just look like sand or gravel, but when you get up close they are full of tiny, sparkling pieces of calcite! They were beautiful in the sun.

It was a gorgeous day and a beautiful place to collect rocks!

UPDATE: See some tumbled calcite here!

Oolitic Sand Field Trip

We read about Oolitic Sand on the Utah Geology website. It is sediment formed similarly to cave pearls, which we became interested in at Carlsbad Caverns. Oolitic sand starts with a tiny bit of sediment that, as it's tossed around in the water, becomes coated with minerals precipitated out of the water. As it continues to move around in the water, the minerals form around it layer upon layer, until it becomes a little round "egg" of mineral-coated sediment. (This explains it better.) At first glance it doesn't, actually, look that different from normal sand (at least not the stuff here at the Salt Lake), but under a magnifying glass or microscope it's pretty cool. Like tiny round pearls! 

It was a really cold, windy day when we took this field trip, but the dark sky and clouds made the desert landscape seem really cool. We felt like we were on another planet or something (the salt desert always makes me feel that way).

Before you reach the dune area, you pass by lots of shallow lake pools, and you can see salt crystals concentrated on the sides of these pools. On a sunny day they really shine.

Another cool thing about going out to Stansbury Island is that you get to go close to the salt concentrating and crystallizing ponds (I think they're for Morton Salt Company, but there may be other companies working there as well). You can also see the huge piles of white salt glistening in the sun, and big dump trucks going back and forth loaded with salt in their beds. It's really cool.

To find the oolitic sand, we followed the directions here. [There is also Oolitic Sand on Antelope Island and other shores of the lake, I believe.] The directions were easy to follow, except that where they say "Travel about 6 miles on this main road until you reach an intersection with a stop sign on the west side of Stansbury Island"--- there is no stop sign at that intersection (anymore?). It's pretty clear that it's the right place, though, because it's the only place there's an intersecting road at all. It's also a little confusing that it refers to a "sandy dune area" if you're expecting large, rolling dunes. These are small sand dunes dotted with plants, like this:

Doesn't it look like another planet?

These little pointy things were so interesting. They were all over on one side of the road, and on closer investigation each one hid some kind of plant or shrub stem (?)---like this:

I don't know what they were!

Small boy all alone in the harsh world

The sand clumped together in these hard, rock-like pieces. You could crumble them pretty easily but if you were careful, you could just pry them up from the ground in sheets like this. The little round oolites are pretty apparent when you look closely!

After we had collected some oolitic sand, we stopped to look at salt crystals too. We loved walking around on the salt flat areas! And we loved the smell of salt in the air.

Every time the sun peeked through the clouds, the effect was dazzling!

And as a bonus, on the way home we got to pass by the huge smokestack that the children all love so much---Abe got a picture of it! :)

More about crystals

Salt crystals from the Great Salt Lake---small and large. Not sure what causes the difference in size. It reminds me of the difference between intrusive and extrusive igneous rock, but there's not such thing as "intrusive halite" is there? :)

In addition to watching crystallization occur in hot ice, we saw examples of it in several other solutions. We talked about the different crystal habits of various substances, and we examined salt and sugar crystals under our microscope.

It's not the first time we've talked about crystals:

We grew alum crystals in eggshells during our Easter Unit

We grew "stalactites" during our Cave Unit

But this was the first time we have made a more in-depth study of them. They are fascinating! We did two very fast demonstrations with salt crystals and epsom salt crystals. You can find instructions for crystal-growing (including how to make larger crystals using a seed crystal, which we wanted to try but didn't get to) all over the internet. We got our instructions from this page, and from the Happy Scientist.

Cardboard soaked in supersaturated salt solution. We put one outside in the (cool) wind and one inside in the oven.

As you'd expect, the crystals which formed undisturbed grew bigger and more quickly

We loved these branching snowflake-shapes that formed on the edges

These are Epsom Salt Crystals

These are crystals that form when you freeze orange juice

We took a field trip out to the Great Salt Lake (we were actually hunting for oolitic sand, which I'll show in another post) and stopped to observe Salt Crystals along the edges of the lake. We've been to the Salt Flats, and they're amazing, but you can get some of the effect closer to home (our home, that is) near the Morton Salt Plant. There are several areas you can stop by the road and walk out onto the salt. Sometimes it's a bit mushy, but dry enough at the edges, and the crystal formation is amazing!

Beautiful!

A few more resources for learning about crystals:

This video tells about cutting diamonds (and making them into jewelry)

Pink diamonds!

More about diamond cutting (it's in the first segment of this video).

I found this explanation of nucleation helpful.