Is this anthracite coal ?

[Denis Arcand]

I recently found this rock, it is very light, the texture and weight are almost like pieces of plastic, I found several pieces in the same place?

The formation is Ordovician, could it be something else ?

 

If it is coal , it was surely deposited by someone,

 

 

[Yoda]

We used to have an anthracite coal burner when I was a kid

My chore was to fill the bucket from the store outside and bring it indoors. Seem to recall it being quite heavy. 

[FranzBernhard]

Anthracite has a density of about 1.5 g/cm3. Usual rocks are around 2.5 to 2.8 g/cm3. A bucket with coal is stille quite heavy.

 

@Denis Arcand, whats the streak of the specimen? Try to ignite it with a lighter or candle.

 

Franz Bernhard

[Denis Arcand]

2 hours ago, Yoda said:

We used to have an anthracite coal burner when I was a kid

My chore was to fill the bucket from the store outside and bring it indoors. Seem to recall it being quite heavy. 

The weight can seem different when you're a kid; it may feel lighter now that you're an adult. 

[Denis Arcand]

On 10/2/2024 at 5:30 AM, FranzBernhard said:

@Denis Arcand, whats the streak of the specimen? Try to ignite it with a lighter or candle.

 

it's  shiny and black, it has a glassy /plastic like appearance

I try lighting it with a lighter for 1 minute or more, it didn't do anything,

the streak test is dark but more brown than black

it sink when put into water

it is also very hard to scratch with steel nail (Mohs hardness = 6.5)

 

the specific gravity is approximately 1.5  (didn't  have a balance ,  it weight approximately the same as 1/4 cup of water)

 

Edited October 4 by Denis Arcand

[Denis Arcand]

A very dark and shiny material and difficult to photograph, here's another angle with the texture

[FranzBernhard]

Weird!

The high hardness is very puzzling! Low density, brown streak - I am lost!

Franz Bernhard

[Denis Arcand]

  Thanks @FranzBernhard

Edited October 4 by Denis Arcand
duplicate entry

[Denis Arcand]

2 hours ago, FranzBernhard said:

Weird!

The high hardness is very puzzling! Low density, brown streak - I am lost!

Franz Bernhard

It resembles hard plastic so much, leading me to suspect it could be black bakelite, one of the earliest synthetic plastics before being replaced. With a density of 1.5, I recall seeing backlit objects made from this very hard plastic when i was younger. I found other pieces nearby and plan to return to search for distinctive features that indicate it was man-made.

Edited October 4 by Denis Arcand

[FranzBernhard]

Would bakelite not be "toasted" or "roasted" in a lighter flame?

And is bakelite really that hard?

Franz Bernhard

[Yoda]

Obsidian ?

[Denis Arcand]

8 hours ago, FranzBernhard said:

Would bakelite not be "toasted" or "roasted" in a lighter flame?

And is bakelite really that hard?

Franz Bernhard

I suspect it might be Bakelite  because it is a plastic that doesn't soften or melt when heated. It's a hard, an can withstand temperatures up to 285°C. I remember using Bakelite in my youth while working on electronics projects, as circuit boards were commonly made from it. From my experience, I found that Bakelite resists soldering and is exceptionally tough.

[FranzBernhard]

Yes, but 285°C isn´t that much, there should be some reaction (charing etc.) after 1 minute in a lighter flame.

Pure bakelite is quite brittle, if its tough, its reinforced with something.

 

Anyways, a proper specific gravity test is a possibility?

 

Franz Bernhard

[Denis Arcand]

35 minutes ago, Yoda said:

Obsidian ?

I also considered obsidian, but it's generally heavier, with a specific gravity of around 2.5, and typically has a translucent glass like appearance. Additionally, I haven’t observed any signs of volcanic activity in the area, and I've only found a couple of pieces. I have to go with the evidence:

 

• Resembles hard plastic
• Not translucent
• Doesn't burn
• Specific mass = 1.5 
• Brown streak ( Bakelite is basically a very dark brown not black)
• Mohs hardness = between 5.5- 6.5 (not as hard as glass)

 

I’m disappointed. I had hoped to add it to my rock collection, but if it turns out to be man-made, I'm not so sure.

Edited October 5 by Denis Arcand

[Denis Arcand]

13 minutes ago, FranzBernhard said:

Yes, but 285°C isn´t that much, there should be some reaction (charing etc.) after 1 minute in a lighter flame.

Pure bakelite is quite brittle, if its tough, its reinforced with something.

 

Anyways, a proper specific gravity test is a possibility?

 

Franz Bernhard

 

Thanks @FranzBernhard I'll try heating it longer,  and yes , your absolutely right my gravity test was doubtful

 

Edited October 5 by Denis Arcand

[Mark Kmiecik]

On 10/3/2024 at 7:01 PM, Denis Arcand said:

(didn't  have a balance ,  it weight approximately the same as 1/4 cup of water)

 

With or without the cup? Porcelain cup or styrofoam?

[Denis Arcand]

47 minutes ago, Mark Kmiecik said:

 

With or without the cup? Porcelain cup or styrofoam?

No kidding you're asking! It was a very scientific measurement . I used two identical, very light plastic containers. I asked two other person to compare the weight, holding one container in each hand with their eyes closed. We all agreed that the weight was equal to 1/4 cup of water. 

 

Thank you for your interest in my measuring tools. 

 

I will redo the measurement correctly and I will come back with the precise density

Edited October 5 by Denis Arcand

[Denis Arcand]

I found a second piece today, if it was a man made object it doesn't look like it anymore

Edited October 5 by Denis Arcand

[Denis Arcand]

my son is convinced that it is graphite, what do you think ?

[DPS Ammonite]

Way too hard to be graphite which is 1-2.

 

What is the Ordovician formation that it is from? Do you see it in the outcrop? 

[Denis Arcand]

 

36 minutes ago, DPS Ammonite said:

What is the Ordovician formation that it is from? Do you see it in the outcrop? 

 

It is at the top of the Nicolet River formation, not in the formation as is, hidden in vegetation much closer to the street

 

[Denis Arcand]

I bought a scale today,

 

the first rock is 52g/46ml = 1.17 g/ml  +- 0.03

the second is 70g/48ml = 1.53 g/ml  +- 0.06

 

Now, why density differ between to two rock ? 

 

Edited October 6 by Denis Arcand

[FranzBernhard]

Very good!

Impurities or air bubbles. How did you measure the volume?

At least we know now, its something organic.

Especially the second piece would easily pass for some weathered subbituminous (!) coal from my area. But these are much softer!

Franz Bernhard

[Denis Arcand]

5 minutes ago, FranzBernhard said:

Very good!

Impurities or air bubbles. How did you measure the volume?

At least we know now, its something organic.

Especially the second piece would easily pass for some weathered subbituminous (!) coal from my area. But these are much softer!

Franz Bernhard

 

the balance is not very precis , i replace my measurement by an average density

the volume was calculated by submerging the rock in water and measuring the difference in ml

[Mark Kmiecik]

1 hour ago, Denis Arcand said:

Now, why density differ between to two rock ? 

 

It looks like the second specimen has brown(ish) inclusions which may be iron. That would kick up the relative density. Also the second specimen has less of an anthracite look to it.