Dot Physics

I need a little rock help

Maybe this isn’t that mysterious. However, quite some time ago my daughter found this rock in the backyard. First, you must understand that this is an odd occurrence. In this part of Louisiana, there really aren’t any rocks, just dirt. When she showed it to me, I readily dismissed it as some lava rock from someone’s garden. That was the end of the story until a year later when she found it again. This time, I held it and realized it was way too dense to be a a normal lava rock. Holding it up to a magnet, I found that there was some interaction.

Skip forward a little bit of time. I had some people that know a little bit more about rocks look at it. Here are some pictures.

i-cae4ed6bf63df8df7db511d451493da8-i_photo.jpg

These are pictures through a sucky microscope (taken with my phone)

i-61dbabc7ca7c125ae30a3bd9512635e0-i_photo_1.jpg
i-1a5e9d4e995fd982d372becac1dd720c-i_photo_2.jpg

So, what is it? I have three possibilities.

Slag

Slag is left over stuff from smelting or other man-made stuff. The only problem is that slag rarely has crystals inside of it. This rock does (see the arrow)

Basalt

Basalt is a type of volcanic rock. Can basalt have iron in it? I am told, yes it can although that is rare. So, there is nothing to say it is basalt expect what would that be doing in my back yard? I looked around in people’s yards and could only find the normal red lava rocks being used. Maybe this somehow got mixed in, but maybe not. Maybe someone had a rock collection and got really angry at their rock. In an attempt to unleash his/her anger, he/she threw the rock in my backyard. It could happen.

Meteorite

This is what I wanted it to be, because I think that would be cool. Also, if it were a meteorite, maybe I could get superhuman powers if I licked it. I know, I know. Everyone thinks they have a meteorite, I have already been lectured. Why can’t this be a meteorite? Well..(from my extensive online reading – in particular, check out meteorwrongs)

  • There is no fusion crust. Basically, this is the outer part of the meteorite that got really hot. It should be shiny. If it is a really old meteorite, then this could be weathered away. However, after interrogating my daughter, it seems she just found it laying in the back yard.
  • Holes. Meteorites can have holes, but it seems this is not too common.

So, there is really nothing that says it can’t be a meteorite, but you never really know unless someone saw it fall from the sky.

Tell me what you think. Maybe you have some good ideas.

Comments

  1. #1 Peter
    November 11, 2009

    Rhett – I think it might be a chunk of slag. Slags can indeed have crystals. One of the things that you point out in the middle photo looks like it might be a sulfide mineral, maybe pyrite, though it’s really hard to tell. See http://www.mindat.org/gallery.php?loc=52739 for some photos of slag minerals. Keep in mind that the photos on that page are not common minerals, so you probably won’t see those exactly. Slags can contain beads of metal (prills), which also might explain some of what you see. The surface in the top photo looks a lot like ropy basalt lava, but I’ve seen slag that looks like that, too. I can’t remember if there are usually vesicles (bubbles) in slag. But where would this slag have come from? Are there metal smelters in your area?

  2. #2 Glen Thomas
    November 11, 2009

    Looks like the slag at meteorwrongs: http://meteorites.wustl.edu/meteorwrongs/m093.htm.

    And the curved parallel lines suggest someone has cut it with a saw.

    I sometimes get bits of rock brought to me in class by excited kids – a streak test (http://en.wikipedia.org/wiki/Streak_test) often helps to identify minerals such as hematite that seem as heavy as iron meteorites, but this looks like it was tossed into the garden rather than from space.

  3. #3 Rhett
    November 11, 2009

    @Peter and @Glen,

    Thanks for the ideas. To answer your questions, there are not any smelters in this area (at least that I know of). Also, the parallel lines are from me. I cut the rock open. I did not do a streak test, but I will try that.

  4. #4 Al
    November 11, 2009

    I’ve seen slag or clinker sold as aggregate for road crush and pathways. This looks like the right size, judging by your standard scale in the 1st photo. The exterior view in the first photo resembles the clinker I’ve seen too.

  5. #5 Dave
    November 12, 2009

    Probably slag, but here are a couple of things to consider. Usually meteorites are either Carbonaceous, or metallic. Rarely do the two forms combine (Why, though? Different formation areas in space?).

    Metallic meteorites are usually composed of Iron and/or Nickle. Do the metal inclusions show characteristics of Iron and or Nickle? Note, though, that the Iron areas may rust into various types of Iron Oxide due to weathering.

    Are there any signs of exterior heating as the item flew through the atmosphere at about 18000 miles per hour? Note though, that the external crust may have weathered away.

    Note that meteorites can be found. My dad found a 10 pound (or so) metallic meteorite on his farm, with it being composed mostly of Iron and Nickle!

    Dave

  6. #6 weathercast forecaster
    March 26, 2011

    Basalt is a type of volcanic rock. Can basalt have iron in it? I am told, yes it can although that is rare. So, there is nothing to say it is basalt expect what would that be doing in my back yard? I looked around in people’s yards and could only find the normal red lava rocks being used. Maybe this somehow got mixed in, but maybe not. Maybe someone had a rock collection and got really angry at their rock. In an attempt to unleash his/her anger, he/she threw the rock in my backyard. It could happen.