Monday, 5 December 2011

Glorious gems and other earth treasures ~

Sodalite
Planet Earth contains an astonishing and very beautiful range of gems, minerals and other treasures.  In this chronicle I look at a selection I'm familiar with and briefly describe their physical characteristics and, where possible, the geological context in which they were formed.  As I've learnt more about them I've enjoyed and appreciated them more, so am happy to share that.

Mussel shell - note tiny crab
I've been picking up stones ever since I was a little girl, mostly specimens of unremarkable grey shingle but carefully picked out all the same.  I have no recollection of this but my mother tells me this was a pre-occupation on my walks, so there it is!   

When older I took up the interest once more.  I still look for interesting stones on my walks, and when wandering along beaches I also look for shells.  However, most pieces included here have first been found by others, some locally, others far away.  They have been gathered and dispersed by these collectors long before I set eyes on them, so I'm grateful for their interest which has made it possible for me to indulge my own!

Amethyst with citrine inclusions

This Chronicle is designed to be read from the top down throughout its entirety, although each entry can be read by itself without reference to others.

Amber

Sunday, 4 December 2011

Sequence and layout of articles ~



After a great deal of reading, sorting of geological information and experimental groupings I've arrived at a sequence that I think makes good sense.  Each group has been allocated a month of the year, which I outline below.  Please note that the Chronicle has to be set out in reverse chronological sequence due to limitations of the blogger format:

Part of what I want to share with this chronicle is an understanding of the sorts of processes and minerals that have formed the surface of our planet.  The sequence shown here is my effort to make this relatively clear.  I'm no geologist, so won't get it right all the time but despite this have made every effort to sift through and make sense of information from reputable sources.  Constructive comments and corrections are welcome.

The planet's rocks fall into three main groups so I'll start with them.  The three types of rocks are:
  • Igneous rocks - which have resulted from volcanic activity.  (These articles have been placed in November)  I've expanded this to include minerals and formations that are associated with hydrothermal activity.  This group includes obsidian, sodalite, moonstone and others.
  • Metamorphic rocks (October) - These have been subjected to immense pressures, heat, and possibly chemical interactions as well, which have changed them from the structure they once had.  This group includes jadeite, serpentine, quartzite, and others.
  • Sedimentary rocks (September) - these have formed from layers of minerals and detritus having drifted down and accumulated over very long periods of time - usually in water.  This group includes sandstone, azurite, and selenite, to name a few.
The subject of sedimentary rocks with its focus on the watery depths leads on to the subject of other...
  • Watery treasures (August), and indeed the chemical content and temperature of the waters themselves, primarily sea water, so the next section is about this.  Articles in this section include pearls, coral, shells, and the related topic of calcite and aragonite from which shells are formed.  This last matter had me baffled for a longish stretch when I was doing the reading for this section, and I want to make this easier for others to grasp!
The next section is about silicates, which occur in all kinds of rocks.  It's a big topic so I've divided it into chunks: 
  • Quartz crystals, pebbles and obvious variations (July), for example, amethyst, rose quartz, and smoky quartz.
  •  Agates and jaspers (June) : such as carnelian, onyx, and tiger's eye.
  • Other silicates which are transparent or semi-transparent (May), such as topaz, garnet and emerald.
Then we have a group of 'other gems' (April):  These include the non-silicates, as well as those which may be rare or unusual, or which I'm simply not yet sure where to place.

Next we have the metals or ores (March), which includes
  • The mica group and others such as pyrite, bornite and chalcopyrite.
All about wood (February), which includes:
  • Amber, petrified wood, and wood itself.
And finally any miscellaneous articles, cogitations and conclusions. (January)
This is where I'll put my article about costume jewellery.

Saturday, 3 December 2011

Gemstone gallery ~ taking it to the next level

Dear readers,
Most of the material I intend to place in this chronicle is now displayed.  I've been very busy placing entries into more cohesive sequences which I have described in the article above, so most of the basic content and structure has now been established.

What I'll be doing next is fleshing out individual entries to include a little more about their geological contexts where I'm able to find this out.  I've already learnt a great deal more about geology!  I will also continue to add to and refine the list of geological and technical terms that I've placed on their own page. 

If entries seem to have disappeared since you last looked search for them in the label index at the lower right of the screen and click on these links - they will take you straight to whatever it is you're looking for.

I've included the image of the little brooch as something for you to look for in an article yet to be published - about costume jewellery.

Thursday, 1 December 2011

Gems and crystals ~ supposed magical and 'healing' properties

A quick search of the web for anything about gems and crystals immediately brings forth a torrent of items about their supposed healing qualities.  You will  not find anything of that sort on this site.  

At one time I was closely involved in this aspect of gems, and now see it as vastly over-stated and misleading.  I am 'sensitive' to what I perceive as the energy and atmosphere of certain stones, but I no longer attribute healing qualities to them.

Home baking is yummy!
In my view anyone seeking such help is likely to get better value from a well made cup of tea and a slice of good fresh cake (or biscuit!) shared with someone who will listen to them intelligently.

What you will find here is a celebration of their beauty, and in addition a scattering of tips about what an enthusiast might look for and be aware of when browsing the shops or wandering along beaches.  In my view gems should be valued for themselves and not as a tool to serve us in any way.  

Links from this site are to neutral sites - mostly Wikipedia - which give insight into scientific and historical aspects.

Tuesday, 29 November 2011

Volcanic activity ~ and the rocks and gems associated with them ~

Rare clear blue obsidian
Rocks from a volcanic source are termed igneous rocks.  In the month of November I've placed entries for all specimens of this sort as well as those that are associated with them.  Also included are those which have a relationship with hydrothermal activity.

The Wikipedia article linked to above provides an excellent introduction.  It states that:
The upper 16 kilometres (10 miles) of Earth's crust is composed of approximately 95% igneous rocks with only a thin, widespread covering of sedimentary and metamorphic rocks.[1]
Note: Obsidian is a form of volcanic glass and usually black.  You can find my brief article about it by clicking on the link below.  It includes a photograph of a snowflake obsidian necklace as well as a larger version of the above image:

Sunday, 27 November 2011

Labradorite and spectrolite ~

Labradorite and spectrolite are both types of feldspar, a mineral formed from volcanic magma.  They are characterised by beautiful iridescence which catches the light and changes as it is moved.  It is fairly brittle.

The pendant displayed at the left has a glassy appearance and is very eye-catching. 

Below is a larger piece.  It's about the size to fit into the palm of your hand.

My understanding of the distinction between labradorite and spectrolite is slight.  The necklace shown here was sold to me as spectrolite.  The beads are nearly transparent.  The little gem at the centre is moonstone, also a form of feldspar, which I will place in a separate article. 


Saturday, 26 November 2011

Moonstone ~

Moonstone is also known as hecatolite.  Its most common form is adularia.  Like labradorite and spectrolite it is a form of feldspar, a mineral that forms from volcanic magma.  It can be many colours and is characterised by the way it reflects light internally.

The gem at the left, which is greatly magnified, is nearly colourless.
The pendant has three lovely soft colours within it: blue, yellow and pink.  The small stone above it is an amethyst.

The beads of the necklace below are more creamy and opaque.

The pinkish brown heart pendant was sold to me as peach moonstone.  It is completely opaque so I'm not sure that this is correct.  

Moonstone, like other gems, includes a wide range of colouration and appearance within its class.  

Thursday, 24 November 2011

Amazonite ~

Amazonite is part of the feldspar family.  Other members of the feldspar family are labradorite and moonstone.  

This small pebble shows the greenish-blue and veining typical of this stone. 

 
It can also be a vivid shade of green, an example of which can be seen by following the Wikipedia link above.

I'm uncertain about the identity of the stone below.  However, I think it is likely to be amazonite as the graduated colours are all within the right part of the spectrum and the veining is also what I would expect.  It's a handsome piece, perhaps about four inches wide.


Tuesday, 22 November 2011

Sunstone and Goldstone ~ pick the genuine one

Goldstone is a fairly common imitation of naturally occurring sunstone.  Goldstone is handsome but artificial, and cannot match the brilliance and loveliness of genuine sunstone.  The range shown in Google images doesn't do this gem justice at all.

Both pieces shown here are artificial.  They were sold to me as sunstone, which didn't bother me at the time but isn't accurate.  If you want the real thing it pays to shop carefully!

I've shown both pieces larger than actual size so that you can see the distinctive sparkle.

Sunstone belongs to the feldspar group.


Sunday, 20 November 2011

Rhyolite ~

Rhyolite is a type of igneous rock, which means it formed through the cooling and solidification of volcanic lava.  

Knowing this makes this mineral rather special for me: the thought that the stone from which these beads were made was once flung from a volcano in a molten state really tickles my imagination, and it seems strange to be wearing such a thing around one's neck!  

I'd be pleased to know which volcano it was and how long ago, but didn't think to ask at the time.  Often retailers don't know this sort of thing, but often they do and can tell you quite a bit, which can add considerably to our appreciation of them.


Friday, 18 November 2011

Obsidian ~

Obsidian is a form of naturally occurring glass resulting from volcanic lava flows.  The wikipedia article linked to here states that:
[it] is commonly found within the margins of rhyolitic lava flows known as obsidian flows.
Snowflake obsidian: 
The article above continues...
...In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian).

The necklace pictured above is the only set of beads I've ever seen made from this material.  I have found it surprisingly pleasing.

Clear blue obsidian:
Look at this!  It could not be more different:


Wednesday, 16 November 2011

Sodalite ~

Sodalite is distinguished from lapis lazuli by its characteristic white steaks, and is royal blue rather than the more purplish blue of the latter. 


Not everyone one would expect to know the difference actually does know.  A jeweller I knew mistook one for lapis lazuli.  

Sodalite fractures fairly easily, so should be handled with care.  Having said that it takes a high polish and is a very pleasing stone to wear.

Look at this glorious globe:  There can be no mistaking the distinctive markings here!



Monday, 14 November 2011

Turquoise ~

Turquoise is a soft mineral and needs to be treated with care.  It's porous and prone to discolouration even from contact with the skin.  When I was considering buying turquoise I specifically asked that it be untreated, but the gem retailer assured me that all good quality commercial turquoise is lacquered - in order to protect the surface.  Without this anything worn against the skin could be expected to rapidly discolour, first to green and then to a nondescript brown.  

I decided to accept the constraint and bought the one pictured below.  The other two necklaces in the picture are azurite-malachite in the centre, and around the outside, calcite or aragonite.  (The jury is still out on this one!)


In the enlargement below you can see that the beads contain small flecks and that the colour varies.  Flecks in turquoise are likely to be pyrite, and any spidery veining, limonite.


The last paragraph of the Wikipedia article linked to above includes this excellent advice about the care of turquoise jewellery: 
Being a phosphate mineral, turquoise is inherently fragile and sensitive to solvents; perfume and other cosmetics will attack the finish and may alter the colour of turquoise gems, as will skin oils, as will most commercial jewellery cleaning fluids. Prolonged exposure to direct sunlight may also discolour or dehydrate turquoise. Care should therefore be taken when wearing such jewels: cosmetics, including sunscreen and hair spray, should be applied before putting on turquoise jewellery, and they should not be worn to a beach or other sun-bathed environment. After use, turquoise should be gently cleaned with a soft cloth to avoid a build up of residue, and should be stored in its own container to avoid scratching by harder gems. Turquoise can also be adversely affected if stored in an airtight container.
Turquoise pebbles
Turquoise is often faked through the use of a variety of different materials and methods.  If you are in one of the cheaper gift shops or even gem shops you may see strings of beads which look like turquoise, but are actually dyed howlite.  This practice is relatively common.  Howlite in its natural state is white, or close to it.  I have written about this stone separately - refer link.

Turquoise is classed as a phosphate mineral.

Saturday, 12 November 2011

Larimar and pectolite ~

Larimar is a form of Pectolite.  These are very small specimens which I bought as a curiosity never having seen them before.  Larimar is found only in one place on the planet - the Dominican Republic in the Caribbean. 


Thursday, 10 November 2011

Sulphur ~

Sulphur is a chemical element and essential for all life forms.  It is present in all proteins and enzymes.  It has many uses, from medicinal to agricultural and is a component in gunpowder.  

This little sulphur 'flower' probably formed in the thermal region of the North Island of New Zealand:


It got a little dusty from being out on display for a long time.  I have since dusted it very carefully with my softest paintbrush and will re-photograph it at some stage.

Wednesday, 9 November 2011

Wavellite ~

Wavellite is a phosphate mineral and is known to occur in a number of different environments, one of them being hydrothermal areas.  This little specimen is about and inch and a half wide and is typical of its kind.


The radial clusters on the second specimen below are smaller but clearly of the same sort:


I don't know where these two little piece came from but they are reminiscent of my sulphur flower which almost certainly came from a hydrothermal are in the central North Island of New Zealand.

Tuesday, 8 November 2011

Hematite


Hematite  is a mineral form of iron oxide.  Used in jewellery its metallic grey can seem a little dull, but this piece is charming and an imaginative combination with the little pearls and gold spacer beads.


Monday, 7 November 2011

Rhodochrosite ~

Rhodochrosite is mostly warm pink in colouration with pale whitish bands through it.  These can be seen clearly in the little egg, and less so in the beads below that.  It is relatively soft and not often seen in shops.  Prepare for it to be fairly costly if you do find it!

The beads are small but the colour and the banding you can see are typical:

Closer detail:


However nice my own photographs are, they pale beside the dramatic images on this site - magical!

Sunday, 6 November 2011

Heulandite ~

Heulandite is one stone I know nothing about.  The specimen shown here is not like what is described in the Wikipedia article, but I did find some images like it in a Google images search.  There is a wide range of structure and colour associated with this name! 


I bought this tiny specimen because I liked it - it seems to have quite a personality of whatever sort it is that rocks have.  It measures about an inch across.

Saturday, 5 November 2011

Tuesday, 1 November 2011

Charoite ~

Charoite is a rare mineral at present known to occur only in Siberia.  Both the colour and the swirling fibrous masses seen in these two specimens are typical of their type.  Both pieces are shown considerably enlarged.



Sunday, 30 October 2011

Metamorphic rock ~ rocks and gems under pressure

Nephrite or greenstone
Metamorphic rock has been subjected to tremendous pressure and possibly heat as well, causing it to change in structure.  The rocks and gems included in the section below have all undergone a metamorphic process of some sort.

The piece of nephrite shown at the left is just such a rock.  It is known as greenstone or pounamu in New Zealand, the latter being its Maori name.  You can read more about it in the two articles linked to here:

Friday, 28 October 2011

Lapis lazuli ~

Lapis lazuli is a notable mineral with a long history of many uses, one of them being as an artists pigment.  It has also long been used for carved ornaments as well as jewellery. 


Like many gems it can easily be faked or coloured to order, so if you want the genuine article it can be wise to do business with a known and respected dealer.  It is commonly flecked with small amounts of pyrite, a gold coloured mineral, as you can see in this detail from the above image:


It can have white calcite inclusions but I've never seen this.  The flecking and colour varies considerably, so an evenly matched set of beads will be more costly than one that is not.  However, they are also more likely to be artificial, so proceed with care as it can be costly!

The charming bracelet shown below provides us with no such qualms: the variation of colour in the lapis pieces included is reassuring, and it was not costly.


Wikipedia states that: 
Lapis lazuli is a rock, largely formed from the mineral lazurite.

Wednesday, 26 October 2011

Jade ~ nephrite and jadeite

Nephrite pendant
The jade group is made up of two different metamorphic rocks:
Nephrite, which is a variety of actinolite, and
Jadeite, which belongs to the pyroxene group.

Until 1863 the two were considered to be the same mineral - jade, but at that time were found to be chemically different.

The term 'jadeite' was then coined to distinguish one form from the other.  (Refer to Kim Howard's article as linked to below.)

In Chinese culture the term jade has been more general and can refer to 'precious/ ornamental stone'.

Nephrite: Of the nephrite group I have already written about New Zealand Greenstone, termed Pounamu, by the Maori people.

Jadeite:  Colours of jadeite include various shades of green through to white, and in rare instance, bluish and violet shades.

"Jadeite" by Kim Be Howard, is a fascinating article for those wanting to read about jadeite in depth.   I found the history of its usage and cultural value in South America particularly intriguing.  Only the inclusion of photographs could improve this publication!

What are the pieces below?  I'm inclined to think they're jadeite simply because I haven't seen nephrite this pale, but am happy to be corrected.  


Monday, 24 October 2011

Greenstone ~ also known as pounamu

Greenstone, known to the Maori people as pounamu, is nephrite jade, a form of jade.  It is special to New Zealanders due to its high significance in Maori culture and also for its own sake.  For many generations Maori used it for personal jewellery, in axe heads for domestic purposes, and also for weaponry. It's a hard stone and fairly heavy.

The simple piece photographed here has a good feeling about it for me. 


Greenstone is a very personal stone to own, and it's important to feel completely comfortable with it as it can have a moody effect on the wearer.  If buying another piece I would always want to meet the carver and have a good feeling about them and the purchase. 

I had a beautiful and ornate greenstone piece which I liked initially but came to feel that it was not quite right for me, so I was pleased to pass it on to someone who I know is delighted to have it.  I liked the man who carved it and he was happy to sell it to me so I was confident that the good feeling would go with it. 

There are many fine carvers in New Zealand and a host of lovely pieces to choose from.  
Paul points out that much greenstone sold in New Zealand tourist shops is made from imported greenstone; some of it is even carved in China.  It is unfortunate that many shoppers get the impression that it is local, so if you want the local product it pays to be sure of your source and possibly to buy direct direct from carvers.  Some years ago when I was enquiring about such things I was told that no greenstone beads were locally sourced as no one in the country had the equipment to make them. 

In this country greenstone only occurs in the South Island where it is often found in the rivers of the West Coast.  The Maori call the South Island Te Wai Pounamu, which means the [land of] greenstone water. 

The story of how pounamu came to be widely known to the Maori is a fascinating one, and you can read it here:
"First over the Alps - the epic of Raureka and the greenstone"
Anyone who knows the New Zealand Alps will be astonished by this story as the Alps are real mountains complete with ice, snow and glaciers, and can be treacherous even for well prepared people of modern times, and this trail blazer was a woman with only one companion!  Let's hear it for Raureka!