[Kara] Schist or Gneiss?

Any geologists reading here?  Please don't be offended that I'm attempting to wade into your territory to discuss schist and gneiss.

We were first introduced to schist rock last week outside of Queenstown as we were driven down Skipper's Canyon Road, a precarious gravel track that leads into Skippers Canyon where the Shotover River runs.

We didn't get any great pictures of the schist in this valley because I didn't realize we would see it again.  But perhaps you can get a hint of the striations through this picture of Lighthouse Rock.  While we stopped to take this picture, we picked up a piece of schist off of the ground and it was very soft--the softest rock I've ever felt.  It looked similar to slate, but we easily scraped off material at the edges with our fingers as if it were wet particle board.  And after we touched it, our hands were covered in a fine glitter powder of mica.  It was obviously sedimentary rock, but our guide called it "sedimentary metamorphic."  What???  I'd never heard of that in 7th grade physical science, so I assumed the man didn't know what he was talking about.

BUT, I owe that guide an apology! 

A few days later, we were hiking a few hundred kilometers away at Franz Joseph Glacier on the west side of the South Island and we saw this very striated rock that looked like schist, but seemed as hard as granite (and there were granite and quartz stones on the ground around it).  So I had to do some research, and . . .

Now I know that sedimentary metamorphic is a real classification for rocks.  In fact, what I don't remember from 7th grade physical science (or didn't learn) is that metamorphic rocks all began life as sedimentary or igneous (or even other metamorphic) rocks and then were subjected to the overwhelming combination of temperature and pressure deep in the earth's crust that metamorphosed them (which changes the crystal structure of the rock, but not the chemical composition of it). So, the soft schist in Skipper's Canyon is metamorphic, but just not as metamorphosed and the harder schist at Franz Joseph Glacier.

The next problem I encountered as I researched was that there's another type of stone that similar to schist--it's called gneiss.  And some of the striated rock that we saw at Franz Joseph Glacier was gneiss (so said an interpretive sign near the foot of the glacier).  But how could I tell the schist from the gneiss?  Apparently, it's tough to do and even geologists can't do it easily all the time (so says the Internet).  Some of the characteristics that determine the difference include slaty cleavage, schistosity and gneissic banding. 

(I don't know what any of those words mean, but they sound amazing, don't they? And I don't care to research this any more and because I'm the homeschooling teacher, I can decide when we've learned enough.)

Kate is leaning against a bolder of either schist of gneiss near the foot of Franz Joseph Glacier.

In case you're interested in learning more, here are a couple of my sources:
http://www.columbia.edu/~vjd1/meta_rx.htm
https://www.gns.cri.nz/Home/Learning/Science-Topics/NZ-Geology/Rock-Types

P.S.  Yesterday we saw the Pancake Rocks of Dolomite Point near Punakaiki that are ALSO very striated.  But they are neither schist nor gneiss.  They are limestone.  According to an interpretive sign at the Pancake Rocks, scientists don't understand how or why they were formed in layers.

Pancake Rocks of Dolomite Point near Punakaiki