Brown Landscape Rock ID?

[FossilNerd]

I came across this landscaping rock on a recent job. I believe that my grandparents also had this same rock in some of their landscaping years ago. It brought back childhood memories of it at least. I think it’s “out of style” now and no longer used.  I’m just curious as to what it is. I’ve searched on the internet to no avail. It’s lighter in weight and tends to break easily as most of it is full of cracks. It is brown on the outside, but is a grey color on the inside. I wish I had a few more pictures, but I didn’t have time to stop work and get better shots. Any ideas?

[DPS Ammonite]

How hard is it; scratch it with a steel knife? Does it fizz in acid? 

[FossilNerd]

8 minutes ago, DPS Ammonite said:

How hard is it; scratch it with a steel knife? Does it fizz in acid? 

Unfortunately, I didn’t get to pick any up while at the site. I wish I had. I was hoping someone else would have used it in the past or be able to recognize it by sight. If I run across anymore (I do from time to time) I’ll get more details and a sample.  

[grandpa]

Hey Wayne.  Hard to say for sure from the photos, but I get a volcanic/lava vibe from what I'm seeing.  I think I see lots of gas vugs from what I can tell, which would account for the low density. 

[FossilNerd]

7 hours ago, grandpa said:

Hey Wayne.  Hard to say for sure from the photos, but I get a volcanic/lava vibe from what I'm seeing.  I think I see lots of gas vugs from what I can tell, which would account for the low density. 

Thanks for the input Tom. I definitely need better photos and a sample to do tests with. It seems like it was used extensively in my area in the past so I was hoping someone would see it and have a eureka moment. I run across it from time to time so I should be able to get some more pics and possibly a sample to play with soon. 

 

I thought it may be a type of volcanic rock as well for the exact reasons you described. It does seem very lava-ish.

[FossilNerd]

So I’ve done some more digging this morning and finally found a couple of local landscaping companies that still sell the stuff, or at least it is still listed on their websites. It is labeled as Solite or Kenlite rock. It’s some type of expanded shale? I’m still researching, but is possibly a type of manufactured lightweight aggregate.

 

Picture from local garden center websites...

 

[FossilNerd]

More research... This type of aggregate (labeled expanded shale) can be shale, clay, or slate. It is heated in a rotary kiln at a high amount of heat. Sources vary on the temp and time, but it seems to be at least 2000 degrees Fahrenheit. The rock then expands and becomes light weight and porous. It’s used in all sports of applications. As a light weight aggregate in concrete, as a soil amendment as it absorbs and holds water as well as increases soil porosity (similar to vermiculite), as a landscape “mulch”, and more recently as a component to green roof systems, and much more. 

 

Its sold under various names depending on the locality. Solite, Kenlite, Haydite, etc.

 

Mystery solved!