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1. Any student up to twelfth grade can submit a crystal in the "Alum" competition. (Teachers can also submit alum crystals for a special "teachers only" competition)
2. The maximum starting material is limited to 100 g for any given crystal.
3. The number of submissions is limited to 3 per classroom or household (two for overall/quality and one for coolest crystal). It is recognized that where several crystals from a school or household may be of roughly equivalent overall quality, and it is difficult to make a choice, it may be necessary to submit several crystals. If more than two crystals are submitted by a classroom/household for the overall/quality category, we reserve the right to preselect two crystals for judging.
4. Each submission will receive a Quality and Overall score.
5. Prize winners in the Overall category will be determined based upon their overall score. All remaining crystals will be re-ranked and judged according to their quality score.
6. Each classroom/household is limited one prize winning crystal per category.
7. The minimum size for any submission is 0.5 g.

Judging Criteria
The quality is judged by experts who will rank the crystals on a scale of 0 to 10. A score of 10 will be given to a perfect gem-quality crystal that fits the ideal crystal structure known for the chemical.

1. The crystal is weighed, and the mass M recorded. The crystal must be a minimum of 0.5 g to be eligible for judging.

2. The quality of the crystal is judged on a scale of 1 to 10, with 10 representing a perfect crystal.
The following factors will be considered in judging quality:
- match/mismatch with crystal type (out of 2)
- presence/absence of occlusions (out of 2)
- intact/broken edges (out of 2)
- well formed/misformed faces (out of 2)
- clarity/muddiness (out of 2)
Total Observed Quality Qo = x.xx (out of 10)

3. The Total Score is then determined as follows:
Total Score = [log (Mo+1)] x Qo

The logarithm of the mass is chosen so that large poor quality crystals don't swamp out smaller good quality crystals. The value 1 is added to the mass so that crystals weighing less than 1 g get a positive score.

A 100 percent yield crystal made from 100 g (Mt) that scores a perfect 10 on quality (Qt) would get a theoretical maximum of:
[log (100+1)] x 10 = 20.04
The actual score is expressed as a percentage of the maximum. The crystal with the highest Overall Score is the winning crystal.

100 x {[log (Mo+1)] x Qo} / {[log (Mt+1)] x Qt} = Overall Score %

For example, the best overall crystal (grades 9-12) in the 2016 contest with 100 g starting material weighed 32.8349 g and had a quality of 8.24. Its overall score was:

100 x {[log (32.8349+1)] x 8.24} / {[log (100+1)] x 10} = 62.88%

USCGC Official Rules
Want to get you or your class started growing crystals?

The deadline for entry form submission is Oct. 1st! Complete the form on our Entry Form page to register and receive your materials.

The Rules page includes all of the rules you need to know before you begin growing your crystals. It also includes a rubric outlining the judging criteria and the grading scheme.

For tips on growing large single crystals, click on the Crystal Growing tab to view our crystal growing guide, complete with tips and tricks from professional crystallographers Dr. Jason Benedict of the University at Buffalo and Dr. Ilia Guzei of the University of Wisconsin-Madison

Be sure to check out our sponsors page for more information on the great people and companies who have made this contest possible.
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