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Identity HelpHelp with inclusions in quartz

1st Oct 2017 16:35 UTCJyrki Autio


These quartz crystals are from Kymi granite stock within Wiborg rapakivi granite batholith, Kotka, Finland. I would like to hear if it is possible to just visually identify these inclusions.

1. FOV 10 mm. This one lacks polishing.


2. FOV 7 mm


3. FOV 15 mm

1st Oct 2017 16:36 UTCJyrki Autio

One more

4. FOV 10 mm.

1st Oct 2017 17:09 UTCJyrki Autio

And one more where green needles are better visible

FOV 10 mm

1st Oct 2017 17:39 UTCRob Woodside Manager

The quartz may allow a Raman ID of the inclusions by subtracting the quartz spectrum. The purple might be fluorite.

1st Oct 2017 19:11 UTCOwen Lewis

Jyrki Autio Wrote:


> I would like to hear if it is possible to

> just visually identify these inclusions.

From most of your images. no. From sharper images with greater depth of field and or records for the site of origin, one can quite often make a good educated guess. The standard work of reference, 'PhotoAtlas of Inclusions in Gemstones' is a great guide. Getting on for 2,000 pages in three volumes and with some 5,000 photomicrographs. The inclusion identifications in this work are all backed by quantative analysis. If nothing else, studying this work makes one very cautious in giving any opinion stronger than 'It looks like' without analytical backup. In a limited number of cases an uncommon euhedral form and.or colour might allow an opinion a little more emphatic. Above all, personal examination of thousands of included crystals, improves one's guesswork over time :-)

In your first pic, I'll guess that:

- The purple stuff Rob guesses as possible fluorite, I;ll guess as amethyst (no indication of a cubic habit).

- Some euhedral quartz in quartz?

- Green-black needles/fibres riebeckite or maybe actinolite?

2nd Oct 2017 07:16 UTCJoel Dyer

Hi Jyrki,

I would venture the following guesses, plus some facts, based on material from the Kotka Murskelouhos locality (microscope and Raman work):

- purplish: fluorite fragments (any fluorescence BTW??)

- whitish / greenish prismatic: tremolite-actinolite or other amphibole

- greenish leafy / blade-shaped: chlorite-group mineral

- dark spherules: some mica group mineral(s)??

You may, just may, also have some apatite among some of the inclusions. This also should be pretty easy to find out.

Many of your inclusions are big enough and not too deep for raman+background substraction.



2nd Oct 2017 16:19 UTCJyrki Autio

Thank you Rob, Owen and Joel for insight,

These are recent finds of ugly quartz crystals, but interesting inside. I'm new to inclusions and try to sort out what is obvious and what is not. The first one is from Murskelouhos Quarry and rest from another quarry few kilometers away which seems to be in contact zone of wyborgite and rapakivi granite. Fluorite is common there too.

Here is what I think:

1. Tourmaline needles and anhedral fluorite are quite obvious. Clear and white inclusions less so. One of the clear looks like quartz crystal, rest are more rounded and do still have a crystalline form.

Rounded corners in these are puzzling. It is not obvious if they are filled with mineral. Can negative quartz inclusion look like that?

All murskelouhos quartzes from this pocket have tourmaline inside and out, more near surface. Almost all have cubic imprints on surface after dissolved fluorite. They also have phenakite and partly dissolved topaz and albite crystallized on surface and all these must have formed after quartz. So far I haven't seen any phenakite, topaz or albite inclusions and those in 1. don't look like any of them unless whitish ones are albite.

2. From another quarry. Black hammocks I thought mica group as Joel suggested but they are hard. About same hardness as quartz and also have a bit undefined border to quartz in greater magnification. Could it be silicified something

3 and 5 Prismatic white ones could be quartz after something. These seem to be replaced by quartz on the surface of the quartz crystal and are hollow when termination has been in touch with outside. Green prisms I have no idea. This one seems also have metallic inclusions possibly arsenopyrite and pyrite. At least these are found elsewhere in quarry.

4. Chlorite in radial growths. Is there another option? There is also white mineral involved, maybe a partial replacement of one mineral to another.

This is just my uneducated speculation and it is good to hear Raman is an option also in inclusions.



2nd Oct 2017 19:43 UTCIan Nicastro

I wouldn't jump to the assumption that the green crystals are green tourmaline unless there are known lithium pegmatites there and that someone has previously demonstrated via chemical analysis that the quarry produced elbaite. I looked up the quarry you listed and it is a pegmatite, but I don't see tourmaline having been reported from there, or any other lithium minerals. Looks like it is a beryllium rich peg, and that purple fluorite seems very common there. You obviously live near there and I am on the other side of the world, so maybe mindat is just lacking the tourmaline info, but honestly those green inclusions look bladed and flat like epidote or clinozoisite. We get epidote-clinozoisite in non lithium rich pegmatites out here in southern California.

2nd Oct 2017 21:51 UTCIlkka Mikkola Expert


The black Murskelouhos-tourmaline has not been accurately specified but with XRD they are probably schorl with some lithium.

The thin prisms are brown or dark green in microscope. Biotite is the main mica but the brown mica in cavities is Fe-Li-mica siderophyllite-polylithionite.

Beryl and bertrandite are rare, phenacite is much more common Be-mineral at Murskelohos and Topaz-quarry.


2nd Oct 2017 21:57 UTCJyrki Autio

Only in first picture there are tiny dark green crystals of tourmaline (schorl) which seems to be missing from Murskelouhos mineral list.

2-4 are from another nearby quarry and green prismatic, not quite bladed crystals are different mineral.

2nd Oct 2017 22:14 UTCIan Nicastro

I realized that now... that the other photos are from a totally different deposit with different geology. Sounds like an interesting area to collect in. Raman could likely ID these large shallow inclusions.

3rd Oct 2017 06:07 UTCJoel Dyer

Jyrki, I should be able to help you out in a week or two, I think, if needed.

Negative crystals and inclusions in quartz can take on quite a variety of shapes, due to varying formation and growth conditions of the host. The form is often flattened, rounded out, elongated and of course decrepatation and replacement of original contents is possible at various stages.

Here is one typical quartz inclusion space that shows partial quartz crystal shape:

Here is one of my favourites, I call it "wine bottle being opened":


"Chlorite" can take the shape of irregular plates, sheaths of sword-like crystals or other forms, and often can be identified using polarised light microscopy. The crystal fragments can be (partially) rather colourful in crosspolarised light, depending on their thickness, instead of just pale, slightly bluish or dark green.



3rd Oct 2017 18:44 UTCRob Woodside Manager

The shape of negative xls and inclusions is mostly controlled by the surface tension or surface energy between the xl and the inclusion. The more energy it takes to pull apart the interface and produce more surface, the inclusions will be rounder. A sphere minimizes this surface and surface energy. If the surface energy is low the corners of the inclusion or negative xl get sharper. If it costs little or nothing for surface energy the inclusion or negative xls will be sharp perfect xls.

3rd Oct 2017 19:03 UTCScott Rider

Wow Joel what a snapshot!!! You can use that wine-bottle shaped inclusion for a Logo or your Mindat user image!! It almost looks like a extinguished neon-sign for a liquor store! Way to capture that, I've been trying to get images of inclusions and came up with the conclusion that I need a better camera!!!

3rd Oct 2017 22:08 UTCOwen Lewis


I certainly wouldn't rule out some player part for surface tension but AFAICS, it is certainly not the only player and, in most cases, not even a major player in the determination of negative crystal and other inclusion shapes. A good place to start in reasoning out what might or might not be so is to set out the terms we use.

Inclusions in a crystal can subdivided as protogenetic, syngenetic or epigenetic relative to the host crystal.

Inclusions in a mineral crystal may be either solid or fluid or both in the one inclusion. Fluid inclusions sub-divide into either the liquid or the gas states. A fluid or fluid and solid inclusions fills a cavity in the host mineral crystal. Such cavities often grow to mimic a form of the host crystal and such are termed negative crystals.

Negative crystals are only rarely exhibit a perfect form. As you say, most frequently their angles are rounded or the form is otherwise distorted. Alternatively, the negative crystal may have some form that bears no relation to the host mineral (e.g. jagged hollow 'platelets' in some emerald).

Where, as is quite common, a solid state inclusion, alone and euhedral or otherwise, occupies a volume within a host crystal, the shape of the boundary must always be determined by that of the inclusion where the inclusion is protogenetic - as is frequently the case.

Spherical negative crystals in a mineral crystal host are said never to be found. Certainly, I have never seen one. They are not infrequent in glasses, both naturally and anthropogenetically formed. They can also occur in synthetic crystals formed by the flame fusion method.

My understanding is that there is still much to learn about the shaping of negative crystals but it does seem truly hard to conclude that surface tension is is the governing factor of form in all inclusions.


3rd Oct 2017 22:11 UTCOwen Lewis

Scott Rider Wrote:


> Wow Joel what a snapshot!!! You can use that

> wine-bottle shaped inclusion for a Logo or your

> Mindat user image!! It almost looks like a

> extinguished neon-sign for a liquor store! Way to

> capture that, I've been trying to get images of

> inclusions and came up with the conclusion that I

> need a better camera!!!


As Joel will explain, your camera does not make any difference in this particular ;-)

3rd Oct 2017 22:19 UTCScott Rider

Yeah, I probably will need a microscope to get images of any consequence!

3rd Oct 2017 22:54 UTCRob Woodside Manager

Owen you are quite right. There is more to it than surface tension, but it is a crucial factor. Notice how self protecting this assumption is. If the corners are sharp the surface energy is low if the corners are rounded the surface energy is high. So no matter what it looks like you can say the surface energy is high or low. I know of no experiments that have ever measured the surface energy of inclusions or negative xls. The results of such experiments might lay bare other factors determining the shape.

So if there's no experimental supp0rt where do I get this idea? From making Lava lamps! With two immiscible fluids at nearly the same density and different thermal expansions put in a tall columnar tube, heated from the base will make a Lava lamp. You can fool with the surface energy by adding some surfactant like detergent. No detergent and the organic oil makes lovely spheres with quickly vibrating surface wave modes when it separates for the trip up the tube to cool, shrink, and sink back to the bottom. Adding detergent destroys the spheres turning the "inclusion" into a towering column that slowly and reluctantly breaks free. As it does so the vibrations slow and persist far longer.

That's an interesting observation that spherical bubbles occur in glass but not quartz. This proves that surface tension is not the only cause of the shape. I'll bet you'll find spherical inclusions in isometric minerals like Fluorite and Halite. I'll bet it is the quartz xl structure that prevents spherical bubbles. Since there's often more area on the prism faces than the terminal faces one could argue that the surface energy is lower for them. So one might expect a negative xl to be elongated in the axial direction for prismatic xls. I wonder if the Beta looking quartz with no prism faces have for some reason far less surface energy in the terminal faces than in the prism faces when it is in the depositing medium?

4th Oct 2017 13:56 UTCOwen Lewis

Scott Rider Wrote:


> .....It almost looks like a

> extinguished neon-sign for a liquor store! Way to

> capture that, I've been trying to get images of

> inclusions and came up with the conclusion that I

> need a better camera!!!

Scott, various lighting options are to the photogrpher as paints and brushes are to an artist. There is a way of lighting mineral specimens (esp. transparent ones) known as 'dark field' lighting. This is pretty much an essential option to have available for inclusion photography. A specimen is held just above a specially designed metal light-well that contained a strong source of illumination. To obtain dark-field lighting, a movable baffle is swung over the light source at the heart of the light well, preventing any light coming directly from it and reaching the specimen.The specimen is thus only illuminated (from 360 deg) by light reflected off the polished circular interior wall of the lightwell, being incident onto a specimen mainly at < 45 deg to the specimen's surface. The effect of this manner of lighting is further enhanced by adjusting an adjustable iris fitted over the mouth of the lightwell, controlling the diameter of the lightspot reaching the specimen.

All lightwells are not created equally effective and a good one is worth its weight in gold to the microscopist/photomicroscopist. A good test for effective darkfield lighting is its use to illuminate a spherical inclusion in glass, as below. Note that the perfect sphericity of the bubble inclusion in this cobalt-coloured glass is made plain by the near-complete 360 deg direction of the illuminating light.

@ Rob,

Yes, one might think that isotropic minerals would tend to have spherical negative inclusions but I have yet to see one. Careful examination under the microscope (with darkfield lighting) all seem to show less than perfect roundness, tending towards the dodecahdral, tetrahexahedral or come other generally round-ish but essentially planar form or mix of forms. My personal experience is that most negative crystals in cubic minerals are non-spherical at a glance. See below for an example of a liquid and gas two phase inclusion in fluorite. The habit of the host crystal from Dal'negorsk, is cubo-dodecahedral I think :-)

4th Oct 2017 15:55 UTCJyrki Autio

This has been an interesting read and good starting point at this field.

One thing I noticed is that MinDat picture search for comparative material does not work well in this context because of wordings used in captions. There are 390 pages of quartz + inclusion but 0 pictures of quartz + amphibole + inclusion and 5 pictures of quartz + fluorite + inclusion.

Scrolling just quartz + inclusion pages and reading captions there are of course more to be found.



12th Nov 2017 17:15 UTCJyrki Autio

Joel Dyer inspected some of my inclusions with Raman.

Green ones in No.3 in first post had good match with epidote. Greyish white, often hollow ones could be what is left after epidote altered / dissolved.

In No 1. there are blue and colorless fluorite like this which looks like it is exploding and colorless one in corner

Most interesting was this which does have closest match with prosopite spectrum (of Murskelouhos confirmed minerals)

FOV 2.5 mm


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