| View previous topic :: View next topic |
| Author |
Message |
Chris Foltz
Joined: 28 Oct 2012
Posts: 92
Location: Maryland
|
 Posted: Nov 20, 2012 19:10 Post subject: Re: Mineral ice specimen |
|
|
ICE 9...
| Description: |
|
| Viewed: |
33674 Time(s) |
|
_________________
stone-cutter |
|
| Back to top |
|
 |
Matt_Zukowski
Site Admin
Joined: 10 Apr 2009
Posts: 737
Location: Alaska
|
| Posted: Nov 20, 2012 21:24 Post subject: Re: Mineral ice specimen |
|
|
What an interesting idea. I don’t know of any studies that directly link the macroscopic structure of ice xtals with the substrates on which they nucleate.
At a micro scale, we know well that substrate structure is important for ice xtal nucleation - the closer the structure of a substrate is to ice, the lower the free energy of nucleation on that substrate. This is why people seed clouds with AgI, which has a structure similar to ice. We also know that as the temperature of a substrate decreases, the ability of ice nucleation to overcome mismatches between ice and substrate structure increases. But if you look at snow flake morphology on a macro scale, it seems to be controlled by the various regimes of temperature and humidity that the snowflake falls through, no matter what substrates the ice xtals nucleated on.
Can you think of any other reasons why you observed different ice xtal morphologies on different substrates? Are darker colored rocks (which may have been warmer) different from lighter colored rocks? Are ice xtals in sheltered areas different from those in more exposed areas? Shelter in this case could mean either shelter from wind or from open sky (the more open sky a surface “sees,” the more radiative cooling that surface will receive).
Interesting.
|
|
| Back to top |
|
|
Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
|
| Posted: Nov 21, 2012 09:04 Post subject: Re: Mineral ice specimen |
|
|
| Matt_Zukowski wrote: |
Can you think of any other reasons why you observed different ice xtal morphologies on different substrates? Are darker colored rocks (which may have been warmer) different from lighter colored rocks? Are ice xtals in sheltered areas different from those in more exposed areas? |
After a week of cold nights, it's now warmer...science is thus thwarted. What started me thinking about all this was that there seemed to be no obvious rhyme or reason: the two darkest crystals - the coal and the garnet - had such different frost growth on them, while the black coal and the light-colored blue tremolite had the similar acicular crystals. The garnet and the tremolite are high SG while the coal is quite light; all the specimens are of similar large size. Their different surface textures might support different micro-environments or have different orientations relative to the night sky -- it could be that the needles formed later in the night than the granules when conditions might have been different. Lots of questions to think about!
I think it will take a long time to sort out all the combinations of factors influencing the frost growth, but it has been fun to watch and to think of analogies to what happens inside a vug over a much longer period of time. I was just reading in the Lithographie Amethyst monograph about the Jacksons Crossroads deposits in which sprays of colorless quartz grew during early environmental conditions and larger stumpy deep purple crystals grew among them later as conditions changed (pg 81)- not exactly analogous, but one thought leads to another. John's earlier thread shows the difference https://www.mineral-forum.com/message-board/viewtopic.php?p=24244&highlight=#24244
Cheers
Elise
_________________
Elise Skalwold |
|
| Back to top |
|
|
Chris Foltz
Joined: 28 Oct 2012
Posts: 92
Location: Maryland
|
| Posted: Nov 21, 2012 12:34 Post subject: Re: Mineral ice specimen |
|
|
Irving Langmuir - Polymorph of water...
| Description: |
|
| Viewed: |
33555 Time(s) |
|
_________________
stone-cutter |
|
| Back to top |
|
|
Carl
Joined: 07 May 2009
Posts: 28
|
| Posted: Dec 21, 2012 15:41 Post subject: Re: Ice crystals in a light-artwork |
|
|
I love water/ice crystals. Hoar frost can be particularly spectacular. Please don't hesitate to attach more pictures!
| Description: |
Ice
Jefferson County, New York
FOV ~4" |
|
| Viewed: |
32767 Time(s) |
|
_________________
Get Out There! |
|
| Back to top |
|
|
|
FAQ 
Register
Log in
Forgotten your password?
