Home

Friday, July 30, 2010

Shale versus Slate

I was feeling pretty cocky and confident about the difference between shale and slate yesterday when Bethany posted the previous rock photos, but then I felt doubtful. What is the difference? I was near 90% sure the flat black rocks we’ve been playing with all our lives (stone skipping contests, decorating sand castles, diving for rocks), were, in fact, slate, but had to research it to find out for sure. Here’s what I found on Wiki Answers (and they have all the answers!):

"Slate is a metamorphic rock whose parent rock is Shale. Slate is composed of microcrystals, and because of its degree of foliation, it cleaves easily into thin sheets or plates. Shale is a sedimentary rock. It can cleave, also. The easiest way to to tell the difference between the two is to smell the rock when it is wet. Shales smell like clay, slates do not."

And then, not two entries below in the list of Google search results (Wiki Answers are first?), I found a very interesting blog called: “Lake Trek: A Thousand Mile Walk on the Beach” kept by writer/adventurer Loreen Niewenhuis from Battle Creek. Fascinating! Loreen walked the whole shoreline of Lake Michigan and wrote about her progress in her blog, along with posting tons of photos and video clips. She finished her walk last September at Chicago’s Navy Pier, but continues to write about her work in progress (a book based on her 1000 mile walk along the beach), highlights and memories from last year’s walk, and even this summer’s re-visits to various beaches around Lake Michigan, including our neighborhood near Antrim Shores. She also writes about current issues pertaining to Lake Michigan: The Asian Carp situation, the recent oil spill on the Kalamazoo River (and what a mess that is!), and other related environmental concerns.

From my initial perusal of her blog, it's clear she's gotten a lot done! She's had tons of press coverage, knows her stuff, and in a recent email exchange, informed me that she walked along the beach in front of our cottage last June (of 09). Who knows, maybe we were sitting on the beach when she passed by!

I had initially hit on an entry about “tumbled slate” (see photo just below) and then found her entry on “Antrim Shale” and “Ellsworth Shale.” The tumbled slate she discovered on Fisherman’s Island State Park near Charlevoix, a five mile stretch of unspoiled beach, not 15 miles from our place, with boatloads of this stuff on the shoreline. Along with a photo of a handful of slate, she writes: “This was the only place along the lakeshore where I came across this unusual stone in this quantity.”


Her other two entries are from this year, when she revisited the beach near Barns Park in Eastport. Apparently there is an “Ellsworth Shale” deposit, not far from an “Antrim Shale” deposit. Ellsworth Shale, she explains, is green in color (top photo below), whereas Antrim Shale is dark gray or black (bottom photo below). I had NO idea!


So, it would seem from her photographs that you can see the difference between slate and shale. I never knew there were shale deposits near Barns Park, and I never knew there were two types, or two colors, each named after nearby communities.

When in doubt about the difference between slate and shale, you can test it by scratching it with a knife. As Loreen explained in her email to me: “shale will score, slate will not.”

For more good stuff on Loreen Niewenhuis, check out her website too:

http://www.loreenniewenhuis.com/1_bio/index.html


blog entry by Sarah Dickerson

4 comments:

  1. So, yeah, Bethy: I'd say what you got there is slate.

    ReplyDelete
  2. Wow! Very interesting blog about Loreen's 1000 mile trek around Lake Michigan. Looks like I'll have some reading to do.

    ReplyDelete
  3. Sarah is at the cottage today collecting stones and she picked up what she thought was slate, I think she's saying that they are the same as in the picture I posted the other day, anyway she took a kitchen knife and scratched it, and it scratched. She also was able to break it in half with one hand, so it must be shale.
    This is a work in progress.

    ReplyDelete
  4. yeah, I picked up a bunch, they scratched, broke, split. But I'm sure some of the pieces I have sitting in my living room are slate. I'm getting so confused!:) I can't break em, and I haven't tried to scratch them, because I'd already sprayed some clear gloss on them (just for me).

    ReplyDelete