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The Shapes of Snowflakes

The Shapes of Snowflakes
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In the Northern Hemisphere at least, the idealised vision of Christmas involves snow. Whilst no one snowflake is exactly the same as another, at least on a molecular level, scientists have none-the-less devised a system of classification for the many types of crystals that snow can form. This graphic shows the shapes and names of some of the groups of this classification.

You might wonder what the shapes of snowflakes have to do with chemistry. Actually, the study of crystal structures of solids has its own discipline, crystallography, which allows us to determine the arrangement of atoms in these solids. Crystallography works by passing X-rays through the sample, which are then diffracted as they pass through by the atoms contained therein. Analysis of the diffraction pattern allows the structure of the solid to be discerned; this technique was used by Rosalind Franklin to photograph the double helix arrangement of DNA prior to Watson & Crick’s confirmation of its structure.

Back to snow crystals: the shapes they form are very dependent on temperature and humidity. This diagram illustrates this fact: simpler shapes are more common at low humidities, whilst more complex varieties of crystal are formed at high humidities. We still don’t know the precise variables behind the formation of particular shapes, although researchers are continually working on theoretical equations to predict snowflake shapes.

The number of categories snow crystals can be categorised into has been steadily increasing over the years. In early studies in the 1930s, they were classified into 21 different shape-based categories; in the 1950s, this was expanded into 42 categories, in the 1960s to 80 categories, and most recently in 2013 to a staggering 121 categories.

This latest study splits the classification into three sub-levels: general, intermediate, and elementary. The graphic featured here shows the 39 intermediate categories, which themselves can be grouped into 8 general categorisations. Each of the intermediate categories  have specific characteristics, which are detailed at length in the research paper this graphic is based on.

The eight intermediate categories shown in the graphic are:

  • Column crystals.
  • Plane crystals.
  • Combination of column & plane crystals.
  • Aggregation of snow crystals.
  • Rimed snow crystals.
  • Germs of ice crystals.
  • Irregular snow particles.
  • Other solid precipitation.

There’s a lot more out there on snowflake structure than described here; if you want to read in much more detail, check out some of the links below. If you’d rather just see some amazing macro images of snowflakes, then check out the photos of Russian photographer Alexey Kljatov.

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The graphic is also available to purchase on the Redbubble site here..

The graphic in this article is licensed under a  Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. See the site’s content usage guidelines.

References & Further Reading

46 replies on “The Shapes of Snowflakes”

Antifreeze proteins include the usual blobby body but on one side suddenly appears a full flat plane of regularly spaced ice crystal matching hydrogen bonding stickiness:

http://proteopedia.org/wiki/index.php/1ezg

…or just full lines of regularity to match ice crystals:

http://proteopedia.org/wiki/index.php/3p4g

-=NikFromNYC=-, Ph.D. in chemistry (Columbia/Harvard)

P.S. How does the exact same snowflake crystal forms appear on all six arms at once? What causes that?! It’s quite odd, down to the very fractals of each arm being the same. You didn’t explain that.

[…] 「特定の形が作られる際の正確な変数については未だに分かっていない」とブランニン氏はブログに書いている。「研究者たちは、結晶の形を予測するための理論的な方程式を導き出すための研究に継続的に取り組んでいるが、まだ未解明の部分が多い」 […]

[…] 「特定の形が作られる際の正確な変数については未だに分かっていない」とブランニン氏はブログに書いている。「研究者たちは、結晶の形を予測するための理論的な方程式を導き出すための研究に継続的に取り組んでいるが、まだ未解明の部分が多い」 […]

[…] However, it seems that this metaphor (usually used by adults to tell children that it is a-o.k to be different) is not entirely true. Caltech has found that small snowflakes (the ones we need high powered microscopes to see) can be similar in shape and design while larger snowflakes (the combination of those tiny ones) will always be different. This has to deal with the fact that hundreds of tiny little snowflakes are combining with each other and large snowflake will be created by the same types of snowflakes shown in this chart created by chemistry teacher, Andy Brunning. […]

[…] From one-page illustrations to massive fold-out charts, the best infographics of the year help you visualize, understand, and gain new insights into a whole lot of information: guns used in mass shootings, the geographic breakdown of the usage of the word “bro” versus “dude,” “buddy,” and “pal,” how much time people spend stuck in traffic in cities around the world, and the different kinds of snowflakes. […]

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