Second Natural Occurrence of KFeS 2 (Hanswilkeite): An Inclusion in Diamond from the Udachnaya Kimberlite Pipe (Siberian Craton, Yakutia)

• Published in: Minerals
• Main Authors: Alla M. Logvinova, Igor S. Sharygin
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2023
• Subjects: diamond; potassium sulfide; inclusion; kimberlite; mantle; craton; Mineralogy; QE351-399.2; Yakutia
• Online Access: https://doi.org/10.3390/min13070874; https://doaj.org/article/47fc0d1fd30f481fab7fe89b124d501b

Potassium sulfide KFeS 2 (hanswilkeite) has been identified in polymineralic inclusions in a diamond from the Udachnaya kimberlite pipe (Siberian craton, Yakutia). This is the second occurrence of hanswilkeite in nature and the first one in mantle-derived samples. Sulfide KFeS 2 is monoclinic, the space group—C 2/c. Its crystal structure consists of chains with K in the interstices. The tetrahedra are centered by iron ions and linked by edges, thus forming chains of [FeS 2 ] frameworks. The strongest lines of the electron diffraction powder pattern are 7.05 Å—(200); 5.34 Å (0 <semantics> 2 ¯ </semantics> 0); and 3.05 Å (2 <semantics> 2 ¯ </semantics> 0), and the angles between directions are <2 <semantics> 2 ¯ </semantics> 0/0 <semantics> 2 ¯ </semantics> 0>—60° and <2 <semantics> 2 ¯ </semantics> 0/200>—30°. KFeS 2 has been found as a discrete phase within polymineralic inclusions consisting of apatite, ilmenite, chondrodite, phlogopite, dolomite, and a fluid phase. The data obtained from the composition of the hanswilkeite (KFeS 2 ) inclusion and other rare minerals (chondrodite, Mg-apatite, Cr-ilmenite) in primary inclusions in a diamond from the Udachnaya kimberlite testify to the important role of metasomatic processes in diamond formation.