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Potassium feldspar family mineral group

Potassium feldspar (K-feldspar) is an informal family of potassium-rich alkali feldspars, including the microcline, orthoclase and sanidine structural forms; it is represented by the mineral_group kind without claiming an IMA-approved group name or a single mineral species. Whitney and Evans (2010), reproduced in the IMA-hosted nomenclature compendium, explicitly labels K-feldspar informal. Freeman et al. (2008) distinguishes these structural forms and the compositional end-member notation from an individual orthoclase phase. This family is distinct from the traded feldspar commodity and potash. The experimental feed below is only author-designated potassium feldspar; bulk oxide composition does not resolve its member species or phase proportions. No criticality designation is inherited.

Microbial & Biochemical Mechanisms (1)

PMA2-2 culture-associated aluminium mobilization from a potassium-feldspar feed

bioleaching Microbial

Associated Organisms: Priestia megaterium (NCBITaxon:1404)

PMA2-2 cultures increased filtered Al concentrations relative to uninoculated potassium-feldspar-feed controls, with accompanying acidification. This is an Al-release assay; neither potassium release nor production of a feldspar or potash commodity was established by these measurements.

Experimental Context & Analytical Limits:
Living Priestia megaterium PMA2-2, isolated from Dracaena cochinchinensis rhizosphere soil in Purple Mountain, Nanjing, China, was precultured in LB for 12 hours at 37 degrees C and 160 rpm, harvested, washed and resuspended in 0.85% NaCl. The other-mineral assays followed the dissolution protocol: triplicate 220 mL flasks with 60 mL sterilized glucose minimal medium, 0.60 g of 75-150 micrometre mineral feed and 0.2 mL of 10^8 cells/mL suspension, incubated at 37 degrees C and 160 rpm, with separate flasks for 12- and 24-hour endpoints. Medium preparation pH was 7.0; its stated composition was 0.015% MgSO4.7H2O, 0.05% Na2HPO4.2H2O, 0.025% (NH4)2SO4, 0.01% KNO3 and 0.5% glucose. Element measurements used ICP-OES after centrifugation and 0.45 micrometre polyethersulfone filtration of a 10 mL aliquot; these are operationally filtered total-element concentrations, without oxidation-state resolution. Feed origin, cleaning procedure and quantitative phase analysis were not specified in the inspected methods and supplement. Table S7 reports 19.24% Al2O3, 60.57% SiO2, 9.87% K2O and 4.51% Na2O, plus minor oxides, for this feed. These bulk data do not justify substituting a microcline, orthoclase or sanidine species identifier.
Curated Evidence Points:
Supplement Table S6 (p11; mean +/- SD, n=3) reports filtered Al of 13.09 +/- 1.13 and 21.48 +/- 2.67 micromol/L at 12 and 24 hours with PMA2-2, versus 0.19 +/- 0.05 and 0.11 +/- 0.05 micromol/L without bacteria. Culture pH was 4.69 +/- 0.01 and 4.60 +/- 0.02, versus control pH 7.00 +/- 0.01 and 6.99 +/- 0.01. Table S6 does not report K; its dash symbol denotes not measured, not zero.
Uninoculated feed controls establish the conditional culture-associated difference, but no pH-matched or killed-cell hematite/feldspar comparator separates acidification from other effects. The acid-buffer comparison, detailed transcriptomics, metabolomics, EPS and biofilm assays concern biotite; their quantitative or causal results are not transferred to this feed. Figure 5 reports a separate 12-hour RT-qPCR response to this mineral; expression associations do not demonstrate gene necessity, and the Discussion explicitly calls for functional validation. No isolated-metal product, whole-feed recovery percentage, mineral-specific mass balance or industrial deployment is demonstrated.

Sources & References

  1. ima_compendium_2019: Schertl, Mills and Maresch, editors (2019 copyright). A Compendium of IMA-Approved Mineral Nomenclature, prepared for IMA2018. PDF p34 reproduces Whitney and Evans (2010), DOI 10.2138/am.2010.3371, Table 1: K-feldspar is labeled informal, while alkali feldspar and feldspar are GROUP. Historical nomenclature evidence, not a new 2019 classification.
    https://cnmnc.units.it/ima_reports/2%20IMA-Nomenclature-e-Booklet-2019-1.pdf (accessed 2026-10-11)
  2. freeman_2008: Freeman, Wang, Kuebler, Jolliff and Haskin (2008). Characterization of natural feldspars by Raman spectroscopy for future planetary exploration. Canadian Mineralogist 46:1477-1500. DOI 10.3749/canmin.46.6.1477; pp1482 and 1488-1489, Figure 5, distinguish structural forms and compositional notation. The author-hosted filename says 2009, but the article is dated 2008.
    https://doi.org/10.3749/canmin.46.6.1477 (accessed 2026-10-11)
  3. dong_2026: Dong, Zhang, Yu, Sheng, He and Sheng (2026). Genomic traits, transcriptional responses, and metabolic activities determine functional divergence in mineral dissolution between Priestia megaterium PMA2-2 and Priestia flexa PMD1-1. Applied and Environmental Microbiology 92(9):e01201-26. DOI 10.1128/aem.01201-26; Methods: Bacterial strains, minerals, and media; Biotite dissolution experiment; Dissolution of other minerals and gene expression analysis; Results: Generalizability; Figure 5; supplement Tables S6-S7 (pp11-12).
    https://doi.org/10.1128/aem.01201-26 (accessed 2026-10-11)
  4. ncbi_pma2_2: NCBI GenBank CM125967.1, Priestia megaterium strain PMA2-2 chromosome; source feature and BioSample SAMN50659134 link inspected 11 October 2026. The species identifier does not identify the strain by itself.
    https://www.ncbi.nlm.nih.gov/nuccore/CM125967.1 (accessed 2026-10-11)
  5. ncbi_megaterium: NCBI Taxonomy 1404, Priestia megaterium, species; taxonomy browser and taxonomy XML inspected 11 October 2026.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1404&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T11:14:04.745666Z codex (GPT-6; codex) CREATE Created potassium-feldspar identity and primary PMA2-2 culture-associated dissolution record with feed, control and causal limits.

Record source: data/records/potassium-feldspar.yaml