Sanidine vs Hematite (planetary science edition)
While plagioclase is the dominant feldspar on Mars, high concentrations of sanidine were measured in the Windjana drill sample by Curiosity in Gale crater but it is present in other drill samples.
Hematite is a common mineral on Mars but is particularly abundant in a feature called Vera Rubin ridge at Gale crater. The presence of gray hematite in one sample suggeste hydrothermal precipitation.
@MineralCup
Round 1 Match 7
Check out Sanidine(4a) and Hematite(4b): https://cds.dl.ac.uk/cgi-bin/rfm/crystalworks_trawl_new?8850_3368_5146
But only Sanidine (that and ten other members of the Feldspar group!) is in https://cds.dl.ac.uk/cgi-bin/cw_page/examples_rocks.html
See entry for 28th February in https://cds.dl.ac.uk/cgi-bin/cw_page/examples_365.html
A nice article on Fe2O3 by Helen Brand - "Hematite: a structure determined by Linus Pauling". Pauling determined the structure in 1925.
#MinCup25 #Hematite #Sanidine #365Minerals #Crystallography365
#Sanidine from the Fish Canyon Tuff is essential to understanding the pace of events in the #Cenozoic
High potassium, quickly erupted and cooled, and old enough to have accumulated sufficient 40Ar from radioactive decay. These crystals calibrate neutron flux for 40Ar/39Ar dating. The 28.2 Ma age of the FCT sanidine has been fine-tuned using #Milankovitch cycles of other ash beds in stable sedimentary basins.
photo from MinDat.org by Dan Polhemus
#MinCup25 Round 1 Match 7: It’s a pair of often-overlooked classics as potassium feldspar #sanidine competes with iron ore #hematite.
Vote: https://www.mineralcup.org/2025/vote/r1m07
Results: https://www.mineralcup.org/2025/results/r1m07
Julia Semprich
Bob McMeeking
Bill Minarik
cobalt
Mineral Cup & Ore Cup