[Clayart] Crystal shape and health

Mon Jul 8 22:39:57 UTC 2024

Joel,
    Whether an atom that is NOT silicon, phosphorous, boron, titanium or
another glass matrix former in glass is held within a fixed atomic
structure such as a silicon tetrahedron, or whether it is outside that
rigid structure in an interstitial space in the glass matrix depends on the
size of the odd atom and also the bond angle of the glass former.
   The silicon atom fits perfectly within the space at the center of a
tetrahedron composed of 4 oxygen atoms. The size of both the Si and O atoms
is not coincidental.  The very strong silicon tetrahedron could not have
formed if it were not for the ratio of the Si to O diameters that permits
the oxygen atoms to just touch each other while the silicon atom just
touches all four.
    It's also important that adjacent silicon tetrahedra bond at a range of
angles rather than at a fixed angle as occurs in crystalline solids.
    Oddball atoms fit easily in open spaces within a silica glass matrix
but fit with difficulty in the place of a silicon atom in the silicon
tetrahedron.
    Looking at videos or models of the atomic structure of glass helps all
this make sense.
          Regards,
               Dave Finkelnburg

On Mon, Jul 8, 2024 at 3:32 PM joel joelfink.net via Clayart <
clayart at lists.clayartforum.com> wrote:

> I love journeys of knowledge!
>
> Thanks, David,
>
> I revisited devitrification armed with the insights from the replies and I
> filled a gap in my understanding of glass.
>
> If I'm understanding correctly, as silica is deposited during volcanic
> activity, it is molten glass, but it devitrifies into its crystalline form
> (via slow cooling), SiO2 covalent repeating patterns. Impurities give us
> the different mineral species of quartz, like amethyst.
>
> For lack of a better term, are these inclusions in the "voids" where the
> perfect bonding became partially asymmetrical, and then returned to its
> previous perfect form with, let's say Fe included in the voids, which
> refracts light into the purple part of the spectrum?
>
> Further reading it appears that my impression is correct, and if I
> understand what I read, they are included by forming their own tetrahedra,
> as in Iron ions bonding with 4 oxygen atoms. Is that accurate?
>
> Joel.
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of David
> Woof via Clayart <clayart at lists.clayartforum.com>
> Sent: Sunday, July 7, 2024 11:00 PM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartforum.com>
> Cc: David Woof <woofpots at hotmail.com>
> Subject: Re: [Clayart] Crystal shape and health
>
> Look up "devitrification of glass" for a good start.     I think I hear my
> Mum calling (ha)......  Seriously with regrets, I must attend to other
> pressing concerns.
>
> Perhaps someone else will kindly enter this discussion.
>
> Misneach,
>
> David
> Woof...............................................................................................................................................................
>
> ***********************************************************************************************
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of joel
> joelfink.net via Clayart <clayart at lists.clayartforum.com>
> Sent: Sunday, July 7, 2024 6:51 PM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartforum.com>
> Cc: joel joelfink.net <joel at joelfink.net>
> Subject: Re: [Clayart] Crystal shape and health
>
> Okay, I have thought more about this. In amorphic silica (glass) the
> bonding system is not regular. In silica deposits, I have assumed that the
> bonding is regular. Am I wrong? If not, what is the difference between the
> irregular bonding angles of glass, and the perfect symmetry of quartz
> crystals? Or, are the bonding angles regular in glass, but missing in such
> a way as to prevent a crystal matrix from forming?
>
> Joel.
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of joel
> joelfink.net via Clayart <clayart at lists.clayartforum.com>
> Sent: Sunday, July 7, 2024 5:01 PM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartforum.com>
> Cc: joel joelfink.net <joel at joelfink.net>
> Subject: Re: [Clayart] Crystal shape and health
>
> >>>Quartz has equally strong SI-O bonds in all directions so cleavage is
> nonexistent.<<<
>
> Thanks! That's very helpful.
>
> Joel.
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of David
> Woof via Clayart <clayart at lists.clayartforum.com>
> Sent: Sunday, July 7, 2024 2:59 PM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartforum.com>
> Cc: David Woof <woofpots at hotmail.com>
> Subject: Re: [Clayart] Crystal shape and health
>
>
> Quartz has equally strong SI-O bonds in all directions so cleavage is
> nonexistent.  Thus it must shatter with an internal eruption of force in
> opposition to the direction of externally applied force.  As also in
> shattered Glass, the resulting fragments are sharp edged shards and bits
> all the way to fine micro bits.
> Interestingly "beach glass" has had the sharpness "tumbled off" by wave
> action in combination with sand.
> Same process and results for the bits and pieces of beach quartz which
> once long-ago had been fractured from larger parent masses of quartz by
> varying geologic forces.
>
> Misneach,
>
> David Woof..............................................my Snarky little
> Raven-Haired Muse is attempting humor regarding the sea producing mineral
> "Beach Quartz" and the "Sea Glass from Quarts" some people create during
> their Midnight to 5 :00 AM "Beach Bacchanals." She is becoming frustrated
> and I think it best to chase her down the catwalk to the dock for an
> attitude adjusting belly-flop ducking in the Rio Ko'Kwel.
> Tide is coming in so in the brackish water the little Vixen is sure to
> float like a wind skittered leaf.   She trained with the Seals, so she is
> proficient in under water combat and similar activities.  (Use your wildest
> imaginings .....to where this afternoon is likely to go..........unchecked,
> untied, unchained.)
>
> P.S. If I don't survive this .....ya'll can come and get my pottery stuff
> <);>0)==}=======<
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of joel
> joelfink.net via Clayart <clayart at lists.clayartforum.com>
> Sent: Saturday, July 6, 2024 9:56 PM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartforum.com>
> Cc: joel joelfink.net <joel at joelfink.net>
> Subject: Re: [Clayart] Crystal shape and health
>
> Joe,
>
> Thanks. That is interesting, I had never thought of this. I know the
> feldspars tend to be classified according to cleavage, like orthoclase, but
> I've only a smattering of reading on geology. Lots of desire, but little
> time.
>
> Why doesn't quartz form cleavage planes? It makes sense intuitively since
> glass is a direction into quartz, with pure quartz being pure glass, at
> least so far as I know. But, assuming that is correct, is there another
> reason?
>
> Joel Fink.
> ________________________________
> From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of
> Joseph Herbert via Clayart <clayart at lists.clayartforum.com>
> Sent: Saturday, July 6, 2024 8:45 PM
> To: clayart at lists.clayartforum.com <clayart at lists.clayartforum.com>
> Cc: Joseph Herbert <josephherbert827 at gmail.com>
> Subject: [Clayart] Crystal shape and health
>
> Hello,
>
> Adding to Ron’s post on silicosis: quartz crystals, of whatever variety,
> show no cleavage planes at all. Thus, quartz, when smashed, breaks like
> glass. As Ron says, conchoidal fractures with many sharp edges. Also,
> quartz doesn’t dissolve in human body fluids. This means if it’s in your
> lungs, it’s not leaving.
>
> Volcanic “ash” has the same fracture characteristics as quartz, but it
> forms, uncrushed, as a sharp glass shards when solidified bubbles in the
> cooling lava burst. All the bubble surface, and especially the thicker
> parts where multiple bubbles join, exist as small sharp particles in the
> ash cloud.
>
> Also, asbestos is a mineral with needle-like crystals that can easily
> penetrate lung tissue when inhaled. Crystal shape and low solubility make
> asbestos dangerous.
>
> In some places road gravel is crushed limestone; this is both good and bad.
> Calcite, main constituent of limestone, has three directions of easy
> cleavage so all calcite particles, no matter how small, will be blocky with
> no sharp pointy parts. Also, calcite should dissolve slowly in the slightly
> acid body fluids of the lungs. On the bad side, some limestones have a
> significant portion of very fine clay or quartz particles. Limestones
> usually form in salt water a long way off shore so only the finest
> particles stay suspended long enough to get there. Some other limestones
> form in basins with almost no sediment from land, except for wind borne
> dust.
>
> I have been thinking about risk tolerance and what I might post about it.
>
> To start with, no, bad, or mis information about hazards leads to decisions
> that hold an unknown amount of risk. Such a decision really indicates
> nothing about risk tolerance since the person/people involved are not
> accurately informed about the range of outcomes they face.
>
> Only slight less bad is a correct risk assessment with a mitigation
> recommendation that is misapplied. An example would be fall protection
> (body harness and shock absorbing lanyard) where the tether length is
> longer than the fall distance. One could argue this is worse than no
> protection because the worker has a false feeling of safety.
>
> If you do have good hazard info and you make a good mitigation plan you can
> then decide how much protection you feel you need. For example, a tree
> trimming task near 220 volt power lines with an electric chainsaw might
> call for extra additional ground on the chainsaw case. You might feel that
> a fiberglass ladder, rubber gloves, and a double insulated saw case might
> make the extra ground unnecessary. In this case, you know the possible
> electrical shock risk and might accept the risk of the ungrounded tool.
> Would you also do the task alone? Having someone there to call for help is
> vital. In industry no one should be allowed to work alone. There are
> hundreds of examples why one should not perform a task with risk alone.
>
> From my limited experience, I think potters may have a higher risk
> tolerance than some other groups. This may be because of frequency of
> performance. In industry, a dangerous job might be performed once a year or
> less. Also that job may be performed by different groups each time. If
> there is a dangerous task associated with firing a kiln, a potter may do
> that task many times each year and is always the person who does it.
>
> Frequency of performance makes one very familiar with the task, which is
> good, but may make one less alert, which is bad. If something unusual
> happens, all that experience may not apply and the performer is required to
> safely preform a new task immediately without planning.
>
> Just some thoughts
>
> Joe
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