THE MINERAL ICE

Chemical Formula: H2O, Hydrogen Oxide
Class: Oxides and Hydroxides
Uses: source of water.
Specimens: Due to the difficulty of preserving and shipping snowflakes, we don't plan to have any for sale!

Ice is not often thought of as a mineral, but it is! Most mineralogists define minerals as having an homogenous chemical composition, with an organized structure and of a natural inorganic origin. Ice fits all these characteristics; it has a homogenous formula, H2O, it has an organized structure, with hexagonal symmetry, it is formed naturally as snow, etc. and it is formed inorganically.

Only natural ice counts as a mineral such as snow, natural lake or river ice, glacieral ice and permafrost. Liquid water does not get the same consideration (as to being a mineral) by most mineralogists because it lacks the crystalline structure of ice. However native mercury is routinely treated as a mineral.

Although no known specimens of ice are sold as mineral specimens, there are scientists that study ice and its crystals for some very important reasons. Questions such as how ice crystals form in clouds is important to weather forecasters and climatologists. Glaciologists study the behavior of ice crystals under extreme pressure and how they begin to flow. Physicists are concerned with ice crystals on other planets where their presence is not taken for granted.

The images on this page are courtesy of Kenneth G. Libbrecht, author of the excellent site and reference on snow crystals at www.snowcrystals.com. The photos on this page may not be copied without his permission.

The photos to the right identify the major types of snowflakes, and are taken from the page A Guide To Snowflakes which describes the growing conditions conducive to each of these formations. Note that the complex shapes of natural snowflakes largely result from the constantly changing temperature and humidity encountered by a snowflake as it forms.

I heartily recommend the website www.snowcrystals.com as it displays dozens of ice crystal images (snowflakes), and provides additional information on the growth and structure of ice crystals, how to grow your own, snow crystal photography, plus related topics. Professor Libbrecht is also the author of several books on snowflakes which may be purchased at his site, including Ken Libbrecht's Field Guide to Snowflakes.

PHYSICAL CHARACTERISTICS:

Color is colorless (snow appears white due to multiple reflections; some ice appears white due to air bubble inclusions).
Luster is vitreous
Transparency crystals are transparent.
Crystal System is hexagonal; 6/m 2/m 2/m
Crystal Habits include generally flat hexagonal crystals, ornately complex when found as snowflakes. Also massive in blocks large enough to actually flow in fluid manner (that's how glaciers move).
Cleavage is absent.
Fracture is conchoidal.
Hardness is 1.5
Specific Gravity is approximately 0.917 (extremely light for any mineral - ice floats in water, of course)
Streak is clear.
Associated Minerals: There are no correlations to ice and minerals that it is found with except possibly iron meteorites (and other meteorites), and this is a reverse correlation. On a deep ice field such as the polar caps, any rocks found are likely meteorites.
Notable Occurrences: include North Pole; Antarctica and most tall mountain chains that contain glaciers.
Best Field Indicators: ice melts above zero degrees C.