Tag Archives: geode

To see the 2013 post where Keira left her comment and questions...

What Stone Is That?- A Follow Up Post for Keira

This photo was supplied by Mrs. Yollis and class.

This photo was supplied by Mrs. Yollis and class.

Hello Keira,

In one of your comments you mentioned you had a plethora of questions. A superabundance of questions is the sign of an inquiring mind. It seems as though your questions have turned from astronomy to geology. As before, your words will appear in bold blue text.

Since the day I found the rock that you mentioned in the post at a camping site, I have treasured it. Recently, I went camping at the same exact site, and I found many more rocks that seem to have some kind of beautiful mineral inside of it. In fact, I collected a rock that is made out of all gem. I am a little disappointed that in comments, you cannot post pictures with the text. If I could, I would take a picture of all the rocks I collected so you could see them for yourself.

You have discovered the reason this blog was formed. I also found comments on blogs generally couldn’t include photos, videos or sound and were limited to only one link. A blog allows it all providing we know about being safe online.

When I stumble upon an interesting rock, I tend to have the instinct to pick it up. I know that you probably have that same instinct too, because you are like a walking encyclopedia, always gathering up new information. I said this because I wanted to know if you have either found or bought any new rocks yet. I also want to know which one you most likely do to collect rocks: Do you buy them from rock sellers more often, or do you collect them on your own outside more?

While I have collected rocks in the field, I am unable to travel as much as I once had so these days I am more often to buy samples if I find them interesting. I have recently added some interesting stones. See if you find these samples interesting…

The first photo shows flourite (calcium flourine) crystals. The green mat they're on have 1cm squares so you can see their size. Each crystal has 8 facets (faces), i.e. they are octahedral crystals. They have not been cut. A collector was selling some of his samples at a local country show.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

In my area, different towns have markets on weekends. When visiting one, I found a man was selling geodes from Queensland. While I already had some, I was fascinated by this sample because it looks as though two fused together when they were formed perhaps 200 million years ago.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Here is one from my collection that has been broken open. They aren't as impressive as my Brazilian geodes but I like the Australian samples because they are from home.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

I have yet a few more questions to ask you. Have you ever found a rock from a volcano? I think it would be most likely that you have because, in one of your posts, you said that you had seen a few volcanoes erupt. If, a couple months later, you had gone down to examine the area near the volcano, and you found a interesting rock, I think you would have kept it and put it in your collection. I know that if I found one, I would definitely keep it.

When collecting any stones, we must be aware whether or not we are in national parks where we are not permitted to collect stones and rocks. There are places where you can collect stones, including igneous (volcanic) rocks. When I can, I have collected stones but I have also bought many.

My favourite item from a volcanic area in New Zealand was collected by me (with permission). It was collected near a fumarole where the sulphur (U.S. spelling: sulfur) crystals were forming. Because sulphur crystals break down and lose their shine if exposed to water or moist air, the below sample has been kept in a perspex box since I found it over 30 years ago. The crystals still shine as you can see.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

I have already written a number of posts on volcanoes. Below are links to some of the first posts written for this blog back in 2012...

Volcanoes Post 1

Scree and Obsidian

Aa and Pahoehoe from Hawaii

Pumice and New Zealand Iron Sands

Geological Hot Spots

New Zealand

Final Volcano Post

Another question is have you ever been in a cave where jewels were growing naturally? I asked that question because I heard on a science show that people can explore caves with jewels in them. I doubt that you have ever been in one, but I can not know for sure until you tell me the answer. If you have been in one, what kind of minerals did you see?

A cave of jewels… what a wonderful thought reminding me of the first time I saw the 7 dwarfs working in the jewel mine in Disney’s “Snow White and the Seven Dwarfs” when I was about your age. I dreamed of finding such a mine back then but I know finding a mine with gem quality stones is hard enough without expecting more than one type of gem. A diamond mine would be nice. 🙂

Below is an item in my collection measuring 5cm diameter across the top. Unfortunately, it is only a glass replica.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I have been in gold mines, coal mines and a couple other mines but the closest to a jewel mine would have been an opal mine. There are mines all over the world where jewels are found, some very unsafe for the miners. I only enter mines welcoming visitors on guided tours.

Perhaps Australia’s most famous jewel mine is the Argyle Diamond Mine in Western Australia. It is an open cut mine where they dig down making valleys not dig tunnels.  Here is a link to their website.

Argyle Diamond Mine

You might know diamonds can be different colours other than clear. Argyle’s most famous colour is pink. Click on the link below to see some of the colours in Argyle diamonds…

Argyle Pink Diamonds

This is the last question I have before the last question I want to ask you. I want to ask you if you have ever mined any type of mineral. If so, what did you mine?

When out hunting for stones, I often have my geologists hammer with me. The pointy end is use to chip into rocks and the flat end to break rocks. You could say I have used this in mining in a small way. The picture is below…

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I have also panned for gold in old gold fields and hunted for rocks, crystals and fossils in many locations.

Gold

Some of this sample has been panned by me. Much was bought.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I bought this sample of gold in quartz from a place called Hill End where there was an active gold mine. I have been in a mine in the area but not the active mine.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

A gold nugget from New Zealand, it is about 1.5cm across.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Fossils

The two fossils below were found by me at a rock fall site many years ago. The first shows a fossilised leaf and the second is part of a fossilised tree trunk.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

 In this sample I picked up, you can see shells in the stone. Rather than fossils, they are still real shells embedded in stone.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I picked up the following shell embedded in rock from an open cut mine.

Shell 30,000 years old

Finally, I want to ask you if you have ever cut a rock open and discovered gems inside?

A gem is a stone used in jewellery so it can be anything from quartz to diamonds, emeralds and rubies. I have found quartz and amethyst in rocks as well as in rivers where they have been washed. Some of my stones are of gem quality but I have never found anything really valuable.

This quartz crystal sample might be of gem quality in part if it was cut but I like it as it is.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

As you said in your post, you do not have a diamond cutter, but have you ever used one? If so, was it hard to cut the stone open?

I have seen them used but I haven’t used one. It’s a skill to be able to cut a stone well. I have stones I collected so I could use them if I had access to a diamond saw. They are known as chert and are reasonably easy to cut and polish but aren’t worth much. My samples have colour bands through them so they might look good cut, shaped and polished into cabachons.

Diamonds are not made into cabachons nor are other gems such as emerald and rubies. They are faceted. This means they are cut and polished to have faces. Turquoise, agate and opal are examples of stone often made into cabachons. Look at the images of assorted cabachons below.

CABACHON SAMPLES

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

A diamond saw is used on most stones, diamond being the hardest stone we can find. It uses a special saw blade embedded with diamonds. Before you think this is a waste of diamonds, most diamonds found are not of gem quality. They are industrial quality. I have seen websites selling these low quality diamonds for as little as $120 to $180 per kilogram.

If you have never cut a stone open, would you ever like to cut one of your stones open?

While I would like to be able to cut my own stones, time to do so and the money to buy the equipment means this isn’t possible. I have broken open some samples to look inside but mostly I keep them as I found them. One of the problems with being interested in so many things is finding the time to do them all but it is fun doing what I can.

Keira also had questions on a geology post. Here are some possible answers...

Curious Keira Asked About Geology

4 Comments

Keira left a quality comment on a blog post.

What Stone Is That? - for Mrs. Yollis and class

Hello Keira,

Your rock has certainly caused much thought as we have tried to uncover its secrets. Science can be like that, a chance to uncover mysteries. After leaving a reply to Heather's quality comment, I found you also left a quality comment.

Here is a link to the information I shared with Heather...

What Stone Is That? - A Follow Up Post for Heather

This photo was supplied by Mrs. Yollis and class.

This photo was supplied by Mrs. Yollis and class.

Now for your comment...

Do I know why your rock looks amber on the outside?

From the picture, I'm not able to see the amber colour on the outside. It may be just the remainder of stone or dirt once surrounding your rock. Look at these photos. The first shows a collection of four geodes, one complete. The second shows a geode containing amethyst (mauve quartz). If you look closely, you can see the colours on the outside aren't always the same as the colours inside the geodes. There are other minerals probably once from the surrounding rock. Did you notice one in the top photo has a yellowish outside?

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

It's also possible some citrine quartz crystals might have started to form on the outside. The picture below shows citrine quartz in the paler rock. We can't be certain unless your rock is checked but, no matter what is on the outside, I found your rock very interesting.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

About Galena

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I like your description of galena. It does look a little like tinfoil. Tin (Sn) is an element as is the metal in galena. Galena is lead sulfide (PbS). It's where we get much of the lead (Pb) we use. Below is the heaviest sample in my collection. It's not the biggest in size but weighs 2500g (5.5lb). The gold coloured part of the sample is iron pyrite. It also contains zinc (Zn) but is mostly lead (Pb) in the form of galena. The small whiter patches on the lower left are quartz. The sample comes from one of my state's major mining areas, Broken Hill.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Click on GALENA and it will take you to a Wikipedia page on galena. You will see where it can be found around the world and in U.S.A..

How do you find out all these facts?

I have been interested in very many subjects over the years. When I see something interesting, I sometimes remember facts and information I think might be useful in an extended comment. As I write, I start looking for more information and learn as I go.

For geology, I have assorted books and I can also search online. I always try to check the information I share on blogs because I'm not an expert in any area. Like you, I'm a learner. I've just had more time to learn.

Where did you get all these rocks?

Most of the samples I have were bought in rock shops with only some being collected by me. Many come from countries I have never visited. As an example, the big round geode and the one cut in half beside it are from Brazil. While it can be fun searching for your own samples, collectors often have to buy samples of rarer minerals or ones found in other countries. I have been collecting stones and crystals since I was about your age. It's just a matter of keeping your eyes open  in many cases. Look at these...

The first sample caught my attention because I could see crystals in it. Could it be a geode waiting to reveal something special inside? Perhaps I might one day break it open to find out.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

This one is a geode from Queensland. You can see the crystalline mass in it. Perhaps cut and polished, it could look very good but I like it as it was found.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

This rock was very interesting when I found it. You can see it also has a yellowish exterior like your rock but some chips broken off the rock have revealed what could be agate. I suspect this sample could look very impressive if cut and polished. The material inside might look like your rock.  As I don't have access to a diamond saw to cut it, I keep it as it is, a mystery.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

A Hand Painted Geode?

"...Geodes, the first one looks interesting to me. The middle almost looks like it is hand painted. Was the middle polished or was it like that when you discovered it?"

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

I must say this sample looks as though it's the work of an artist. What I believe has happened is, as different minerals have mixed as the crystals formed in a space, different colours were formed. In this geode, crystal growth has filled the space.

I saw this cut and polished sample in a rock shop. It was the pattern you noticed that caught my attention.

In the middle of the rock that is cut open it looks like there is a little nook. Am I right?

 

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

You are a very observant person. There does seem to be a little nook in the cut rock but it is due to the way the crystals have grown inside the geode. Along the inner cut edge, you can see the crystals aren't even like a circle but have some areas thicker than others. This unevenness means some areas extend out over the others. Sunlight on them leaves a shadow below. In the shadowed area, the crystals look much like the small crystals in the middle.

Considering your curiosity and interest in rocks, I hope you keep learning and discovering. A mind with curiosity can be a very powerful learning tool.

4 Comments

I received a question via Twitter...

Do you know what kind of stone this is ?

There was the below photo attached to the tweet...

This photo was supplied by Mrs. Yollis and class.

This photo was supplied by Mrs. Yollis and class.

I like a challenge and, although not always successful, finding an answer. I have an interest in geology but l find I know a little about many things but not a lot about anything. Without being able to hold the rock and look more closely, and without expertise, my first stop was to look more closely at the photo. Here's what I noticed...

The stone was white to bluish-grey.

Breaks around the edges looked a little like they might break off in flattened, sharp edged pieces.

There appears to be an inner border (lining) on the stone.

I wanted to see the border closer so I enlarged a section of the photo (below). I also enhanced contrast and colour a little.

This photo was supplied by Mrs. Yollis and class.

This photo was supplied by Mrs. Yollis and class.

 I now noticed there seems to have been some fine layering around the edge of the stone up to the border. Layering can mean sedimentary rock but, it can also be a sign of a space in rock filling with crystals. I had seen something like this before. I probably have a few hundred small mineral samples in my collection so I started to search. Firstly, a display of stones I had used with classes over the years...

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

A few of these showed some of the features I was looking for, especially calcite, agate and quartz.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

This reminded me of larger samples I had in my minerals database, I found items 41 and 46. They are listed as "Quartz - Chalcedony - Agate". They are examples of silicon oxide (SiO2).

The first sample has been cut and polished. The layering towards the outer edge is easy to see. There are small quartz crystals in the centre of the sample. I have seen this in other of my samples where inner spaces aren't completely filled. See geodes and the additional photos at the end of this post.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

The second sample was a piece broken off a larger sample and only had a low sheen.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Without being able to hold and examine the sample in Mrs. Yollis's class, I suspect they have a sample of agate or chalcedony. Remember, I am only interested in geology and not an expert so I'm really only guessing.

How is it formed? My database explains it this way...

A concentric, banded, fibrous variety formed by precipitation from watery solutions in rounded cavities in lava rocks (geodes), sometimes with beautiful clusters of rock crystals or amethyst at the centre.

From my collection, below are photos of geodes. Most have been cut and one polished to show the interior.

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Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

The last photo shows one cut sample and an uncut geode beside it. What's inside the uncut geode? I can tell you it is about the same size as the cut geode if it was whole. This means the uncut geode should be about twice the weight of the half but it is around three times the weight of the half. It may be solid or have a small central cavity. It could be very beautiful or possibly plain inside. We'll never know because I won't have it cut. I like a little mystery in the world. 🙂