Strange rock

[Herb]

This was dug up from our garden a few years ago. It's about 2 feet long, very hard indeed and quite heavy. Hitting it with a hammer doesn't chip it. I wondered if it had a lot of iron in it, but it has no effect at all on a compass needle, nor does any magnet stick to it, so I conclude that it's not iron.

I've been trying for years to find somebody who knows about geology & rocks & who can identify it, but so far no luck.

Can anybody identify what sort of rock it is?

[Linda P]

I don't have a clue what kind of rock it is, but it sure is a great one.
Looks like it has fossilized plant material in it, maybe?
Linda P

[Herb]

Linda - It certainly looks as though something interesting was or is embedded in it! I've just done some more image searches on the Internet & have read, first that the most common rock is Basalt and second, that Basalt is very heavy, and third that it comes in all sorts of colours & textures including one called Vesicular Basalt. A few of the pictures of Vesicular Basalt have some resemblance to our rock, but I haven't found anything that looks really similar. I'm especially intrigued by the band that runs all the way round the rock, between the top half and the bottom half. At the same time, the surfaces of top half and the bottom half are very similar.

Meantime, it's sitting in a corner of the garden gathering moss -

[govgirl75]

I think it is basalt from the top of a lava flow. The vesicles get distorted because the surface of the flow cools more quickly than the underneath part. The underneath part keeps moving and pulls and stretches the vesicles into different shapes. Normally I think the vesicles are round, almost bubble like in appearance. Basalt is the result of molten rock and minerals. The banding could be the result of a mineral that fell on top of the flow where it was not hot enough to turn the mineral molten. Either the flow could have folded over on itself or a subsequent flow could have gone over the top of the mineral and hardened, encasing the band.
Sorry if this is a simplistic explanation. It has been over 40 years since I took geology courses at university and the technical memory isn't so good any more.
Glo

[Pandora]

That is pretty cool looking. If you wanted to add to your info, maybe you could post the pictures on a geological forum.
You can google that. I found one at About
http://forums.about.com/n/pfx/forum.asp ... ab-geology

Very interesting indeed.

[Herb]

Thanks, Pandora - I'm giving it a try. I went outside and measured it & see that my estimate of it being about 2 feet long was wrong - it's in fact about 14 inches long.

I'll keep y'all informed......

Herb

[Spider]

Thanks, Pandora - I'm giving it a try. I went outside and measured it & see that my estimate of it being about 2 feet long was wrong - it's in fact about 14 inches long.

I'll keep y'all informed......

Herb

So you have a fisherman's eye...

Cool rock anyway, looks good with moss.

[Herb]

Pandora - I went to the forum you suggested.

One poster says that it's an earth rock & that it had other, less durable rock material embedded in it, & that the less durable material has eroded away & this resulted in the hollows & indentations. Another poster's opinion is that it's a meteorite, and that the hollows in it were burned out when it heated up in the atmosphere.

Whatever, it made me take some more pictures of it - http://www.pbase.com/mtu_fulani/curious_rock