Obsidian or volcanic rock?
Welcome guest, is this your first visit?
Member
Discoveries
 
Results 1 to 9 of 9
Like Tree19Likes
  • 1 Post By Bradley Morrison
  • 3 Post By tamrock
  • 4 Post By Back-of-the-boat
  • 4 Post By ToddsPoint
  • 4 Post By Plug N Play
  • 2 Post By Bradley Morrison
  • 1 Post By Red-Coat

Thread: Obsidian or volcanic rock?

« Prev Thread | Next Thread »
  1. #1
    us
    Apr 2020
    Wisconsin
    8
    16 times
    All Types Of Treasure Hunting

    Obsidian or volcanic rock?

    I found this rock near a quarry in Wisconsin. It is very close to Lake Michigan. It weighs about 0.3 pounds and it has a black-dark green color to it. In some areas in is very shiny like glass but in others it is almost like concrete. It is not slag and it is not magnetic. The dollar coin is there for size. It is rather hard.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	27A73EF2-3B2B-4416-9631-F8A20280D2BA.jpeg 
Views:	26 
Size:	3.55 MB 
ID:	1861971   Click image for larger version. 

Name:	002C2FAF-7C89-40A4-8C2D-0B4299508F51.jpeg 
Views:	18 
Size:	3.83 MB 
ID:	1861972   Click image for larger version. 

Name:	F655FF50-A9A7-44A2-A09C-3F5C4ED82984.jpg 
Views:	20 
Size:	2.53 MB 
ID:	1861970   Click image for larger version. 

Name:	2D6ECF9A-AED1-49F6-A68A-9196D3C0DB24.jpeg 
Views:	17 
Size:	3.52 MB 
ID:	1861973   Click image for larger version. 

Name:	A5420171-49DB-4C72-8F25-424B303E5B0A.jpeg 
Views:	20 
Size:	3.51 MB 
ID:	1861974  

    ToddsPoint likes this.

  2. #2
    us
    Grant Brandenburg

    Jan 2013
    Colorado
    Bounty Hunter Tracker IV
    12,172
    21237 times
    All Types Of Treasure Hunting
    Well it does look like Obsidian rock to me, but slag can look like Obsidian also. People find slag in just about everywhere a Railroad went, because the slag heaps produced by the steel refineries was a great source of aggregate for railroad ballast and that crushed slag got spread for miles across the country.

  3. #3
    us
    steve andermatt

    Apr 2013
    California
    AT GOLD/Garrett /Garrett pro pointer/ 5x8 double d coil and sniper coil/Lesche digger
    5,031
    4809 times
    All Types Of Treasure Hunting
    To me it looks like glass slag just my opinion.
    back of the boat

  4. #4
    us
    Mar 2018
    Todds Point, IL
    2,776
    5109 times
    Metal Detecting
    It looks like slag. Also, obsidian IS volcanic rock. Gary

  5. #5

    Aug 2014
    California
    De Havilland Canada DHC-7-102 Dash 7 - Fugro
    1,097
    2639 times
    All Types Of Treasure Hunting
    We need to see a picture with it held against a bright light.

    This is very generalized
    , and there is the possibility of overlap, here ...
    But the best indicator I've found to distinguish the glass from the obsidian is to go by the color that shows when it's held against a bright light.

    Click image for larger version. 

Name:	Greens.jpg 
Views:	13 
Size:	58.4 KB 
ID:	1862655
    I'm beginning to realize I've gone through life without knowing what anything is ...

  6. #6
    us
    Apr 2020
    Wisconsin
    8
    16 times
    All Types Of Treasure Hunting
    There are some pictures of it right next to a bright light.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	image.jpg 
Views:	9 
Size:	2.34 MB 
ID:	1863345   Click image for larger version. 

Name:	image.jpg 
Views:	6 
Size:	1.96 MB 
ID:	1863346   Click image for larger version. 

Name:	image.jpg 
Views:	6 
Size:	1.82 MB 
ID:	1863348  
    Digger RJ and Red-Coat like this.

  7. #7
    Charter Member
    us
    Randy

    Aug 2017
    SW Missouri/Oklahoma
    Minelab CTX 3030; Minelab Equinox 800
    8,422
    16172 times
    All Types Of Treasure Hunting
    Honorable Mentions (1)
    Looks like obsidian to me.
    AviTech Associate
    The Cygnus 1X

    What would life be without challenges, and detecting of course.....

  8. #8
    gb
    Dec 2019
    Surrey
    1,218
    3192 times
    All Types Of Treasure Hunting
    I see one enormous vesicle and numerous smaller ones. Not obsidian, but man-made glass (slag or frit).
    Back-of-the-boat likes this.

  9. #9

    Aug 2014
    California
    De Havilland Canada DHC-7-102 Dash 7 - Fugro
    1,097
    2639 times
    All Types Of Treasure Hunting
    First, the aside. I'm speaking of colors, and we are currently in the middle of barbecuing California. I apologize. The sun is a weird red disc in the smoke, and you may see ashes in the pics. Colors look off a bit in my pics because of this.

    The black green color you mention shows up in none of your pictures.
    That's what I'd go by is the color, as a way of trying to separate green obsidian from glass.

    We're not going to be able to determine this, but I took some pictures to help you study your piece.
    Let's limit this to two terms ... opaque-we can't see light through it ... and translucent-we can see light through it, no matter how little.

    "Against" a light we should see a hint of green/gold, if the obsidian has any translucency and can be described as green. (my pic is poor, it helps in person because you can wiggle it around) (This is obsidian with a hint of gold/green)

    Click image for larger version. 

Name:	DSC04771.JPG 
Views:	7 
Size:	100.8 KB 
ID:	1863378

    I've never seen obsidian in the bright colors I spoke of earlier. If I see bright green, either opaque or translucent, I tend to lean towards glass. This is glass.

    Click image for larger version. 

Name:	DSC04772.JPG 
Views:	8 
Size:	96.4 KB 
ID:	1863379

    Vesicles mean nothing. If man can melt it, let's not underestimate the power of volcanoes.
    This is opaque green obsidian. Volcanoes have no problem making vesicles.

    Click image for larger version. 

Name:	DSC04768.JPG 
Views:	7 
Size:	233.5 KB 
ID:	1863382

    This compares translucent glass which has colors I've never seen in any obsidian. (rainbow obsidian is a whole different thing, yours isn't, that's an entirely different issue and we can eliminate that, I believe) The blue/green piece is actually opaque green, but still exhibits the brightness I'm stressing in the color.

    Click image for larger version. 

Name:	DSC04775.JPG 
Views:	7 
Size:	236.2 KB 
ID:	1863383

    Anyway, it's the type of GREEN I go by as the biggest clue, and, so far, we haven't seen any green.
    You're going to have to interpret the green you think you see and determine if it falls into a bright green color as I'm trying to suggest, or does it show a hint of gold/green around the thinnest edges when held "against" a light.
    That, I believe will be your biggest clue, while not being definite.

    If you're up to it, break off a shard of this rock and you'll have a very thin piece that tapers to nothing. Backlight it and see if it gives you any more clues as to color.

    As shown in your pictures, I lean towards slag glass (mostly because of locale) ... but would never exclude obsidian without further investigation.
    I'm beginning to realize I've gone through life without knowing what anything is ...

 

 

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Similar Threads

  1. Volcanic rock?
    By Daprezident661 in forum Rocks/Gems
    Replies: 11
    Last Post: May 26, 2015, 07:07 AM
  2. Volcanic rock
    By minermatt in forum Today's Finds!
    Replies: 2
    Last Post: Sep 19, 2014, 09:03 PM
  3. Volcanic rock
    By dawnhvr in forum Rocks/Gems
    Replies: 1
    Last Post: Oct 02, 2013, 08:28 AM
  4. Hot Volcanic Rock?
    By Calvin.Coin in forum Metal Detecting
    Replies: 5
    Last Post: Oct 09, 2012, 09:36 AM
  5. volcanic glass (obsidian) lake taupo new zealand.
    By Des from down under in forum Rocks/Gems
    Replies: 1
    Last Post: Aug 28, 2009, 04:57 AM
Powered by vBadvanced CMPS v4.3.0