<p>I can't be definite but my three best guesses are Travertine, Agate and maybe Halite, if it fizzes in mild acid it's Travertine, a form of Limestone, if it dissolves in hot water it's Halite, or Rocksalt, otherwise if it's more or less inert it's probably Agate, an amorphous silicate. I find Halite unlikely, the other two are probably pretty equally likely in that location.</p>

CC BY-SA 3.0
2017-10-17T12:16:33.970Z
Thank you for your answer.  The rock is most likely the agate you suggested.  It does not fizz with acid and is not salt.  It is capable of scratching glass.  Upon researching pictures of raw agates, I found pictures that look just like the rock specimen I found.
BR in MI
CC BY-SA 3.0
2017-10-16T17:14:24.817Z
2017-10-16T17:14:24.817Z
Ash
<p>Stromatolite structure. The graininess a beat up or weathered limestone of some sort. But if it scratches glass it may be dolomatized limestone with some silica grains, enough to scratch glass. Stromatolite is often of chert but I haven't seen chert weathered like this. The layering looks like chert too. It's a puzzle. </p>

CC BY-SA 4.0
2019-07-08T11:55:41.467Z
2019-07-08T11:55:41.467Z
Wayne L Cooley
<p>Stromatolite structure. The graininess a beat up or weathered limestone of some sort. </p>

CC BY-SA 4.0
2019-07-08T11:32:04.960Z
2019-07-08T11:32:04.960Z
Wayne L Cooley
<p>Rock found along northern Lake Michigan, (Charlevoix, MI).  Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the picture, but the rock has a sugary appearance.<a href="https://i.sstatic.net/xNgwH.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/xNgwH.jpg" alt="top view[![][1]"></a><a href="https://i.sstatic.net/fMP5w.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/fMP5w.jpg" alt="cross section"></a> </p>

<geology><rocks><mineralogy>
What is this Lake Michigan rock?
BR in MI
# What is this Lake Michigan rock?

(Asked by: username_0 on 2017-10-15)

Rock found along northern Lake Michigan, (Charlevoix, MI). Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the picture, but the rock has a sugary appearance.[![top view[![][1]](https://i.sstatic.net/xNgwH.jpg)](https://i.sstatic.net/xNgwH.jpg)[![cross section](https://i.sstatic.net/fMP5w.jpg)](https://i.sstatic.net/fMP5w.jpg)

**Tags:** geology, rocks, mineralogy


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## 3 answers

### Answer by username_1 on 2017-10-16. Score: 5 | Accepted answer

I can't be definite but my three best guesses are Travertine, Agate and maybe Halite, if it fizzes in mild acid it's Travertine, a form of Limestone, if it dissolves in hot water it's Halite, or Rocksalt, otherwise if it's more or less inert it's probably Agate, an amorphous silicate. I find Halite unlikely, the other two are probably pretty equally likely in that location.

> **Comments:**
> **username_0**: Thank you for your answer.  The rock is most likely the agate you suggested.  It does not fizz with acid and is not salt.  It is capable of scratching glass.  Upon researching pictures of raw agates, I found pictures that look just like the rock specimen I found.  

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### Answer by username_2 on 2019-07-08. Score: 0

Stromatolite structure. The graininess a beat up or weathered limestone of some sort. But if it scratches glass it may be dolomatized limestone with some silica grains, enough to scratch glass. Stromatolite is often of chert but I haven't seen chert weathered like this. The layering looks like chert too. It's a puzzle.


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### Answer by username_2 on 2019-07-08. Score: -1

Stromatolite structure. The graininess a beat up or weathered limestone of some sort.


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