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How to grade a mineral

Minerals are works of art, each mineral is totally unique and can be judged by a multitude of criteria. Some criteria are subjective (in the eye of the beholder), while others can be quite concrete. This grading system is a guide designed to help collectors assess how any given specimen ranks among its peers.

As a guide, it provides reference points while still leaving open the possibility that a specimen can be beautiful and treasured simply due to the fact that you enjoy its appearance or that it moves you.

It is here that the worlds of art and nature meet.

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How Our Grading System Works

There are two sections to the guide: Section A with five criteria, and Section B with four criteria.

Each individual criteria is graded out of ten, ten being the best possible and most desirable score. Add up all nine criteria and then divide that sum by nine. This will give you an average score.

Of course there are some specimens where specific criteria are not applicable. In those cases, add up your individual criteria scores, then divide by the number of criteria used to get to your average score.

Please note that this guide is to help collectors assess their collections. A high score does not necessarily denote a high monetary value.


Average Scores

9-10 - Exceptional quality

8-8.9 - Very good quality

7-7.9 - Good quality

6.9 > - Not of collectible quality

Section A

Focuses on the quality of the crystal

Section B

Focuses on the quality and relationship between both the crystal and the matrix

iii. Aesthetics

Back to Criteria
Wilensky Approach


This criterion includes the overall appearance or the beauty of the specimen. Aesthetic appreciation will vary from eye to eye, but some basic parameters are universal: crystal isolation or well-defined individual crystals; crystallized matrix; contrasting colors and textures; crystals of differing size and height; three-dimensional viewing angles; and specimens, which (to quote our friend and master collector, Steve Smale) have “good horizons” or in other words, interesting and well-developed top edges where your eye is initially drawn. Just like any work of art, it must have a pleasing aesthetic arrangement to your eye. This is simply a visual reference to the appeal of the mineral as one would look at any three-dimensional sculpture. The intrinsic value of aesthetic minerals is the pleasure you get from viewing them.

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