“What a rock!” So many of us might say this while observing the gem on someone’s engagement ring. But while the compliment is sincere, the terminology isn’t correct! A diamond isn’t a rock, but a mineral: the pure form of a given chemical compound, which in a diamond’s case is carbon. When geologists talk about minerals, they also usually mean compounds that form crystals; if the compound isn’t crystalline, it might sometimes be called a mineraloid. Put these concepts together, and a rock is an aggregation of minerals and mineraloids.
Recognizing different minerals can take a lot of practice. There are more than 5,400 mineral species, and besides being classified by their chemical elements, you can also sort them by tons of criteria, including but not limited to crystal structure, hardness, luster, color, density, and whether or not they contain the highly prevalent element silicon (so silicate vs. non-silicate minerals). So to start with something simple and shiny, we’re kicking off Eyewire Rocks with a breakdown of minerals by their structure— that is, what sort of shape their crystals form!
There are six families of crystal structure:
- Isometric – Eyewirers probably like this kind! Isometric crystals are essentially cubes, where the lengths of all three axes are equal and the angles are all 90°.
- Tetragonal – These are similar to isometric crystals, with all angles measuring 90°; but only two axes are equal length.
- Orthorhombic – These are also similar to isometric and tetragonal crystals, but all their axes are of different lengths.
- Hexagonal – Such crystals still have six faces, but not all of their angles measure 90°. Instead, two axes are of equal length and form 90° angles, while the last axis is of different length and forms 120° angles.
- Monoclinic – These crystals are further “skewed,” with none of their axes being equal, and only two forming 90° angles, with the other forming <90° angles.
- Triclinic – In this irregular family, crystals’ axes are all of unequal lengths, and none of their angles are 90°.
Can you guess which crystal structure describes each of the minerals below? It’s not easy, because how the crystals look on a large scale is more ambiguous than how they appear on a molecular level! But you might get to show off this knowledge during Trivia next week.
While you think about how to accurately identify these crystals, we’ve got some Accuracy Happy Hours happening! All times are EST:
Session 1 – 8:00 AM to 10:00 AM on 2/20
Session 2 – 2:00 PM to 4:00 PM on 2/21
Session 3 – 10:00 PM to midnight on 2/21
HQ will bestow typical Happy Hour bonuses for your work during each of those time frames, but there’s more than that to earn! Check your in-game notifications to see the full accuracy bonus breakdown.
Swag (generously sponsored by @susi): Most accurate player completing at least 20 cubes wins 1 notebook and their choice of a sticker or magnet! Second and third place may each also choose between sticker or magnet.
Mentors: You are still allowed to mentor people during these time windows. Please just use your best judgment as to whether someone is asking you for basic newbie help vs. trying to have you boost their accuracy on cube after cube.
Scythes: Please avoid scything during these time windows. Even though accuracy for this will be retroactively calculated, we would prefer to go with accuracy based on players’ raw tracing. By the time this challenge is scored, don’t worry, admins will have corrected consensus as needed.
Artwork by Daniela Gamba