Feldspar production begins with geological surveys to identify ore bodies with suitable mineralogy. For industrial ceramic grades, the ore must have: naturally high K₂O (for potash feldspar, target ≥10%) or Na₂O (for soda feldspar, target ≥7%), low iron oxide (Fe₂O₃ <0.3% ideally), minimal calcite, biotite, and tourmaline contamination. In India, Rajasthan's Ajmer, Bhilwara, Pali, and Sikar districts host among the world's best potash feldspar ore bodies. Andhra Pradesh and Telangana's Nellore and Khammam districts host high-purity albite (soda feldspar) deposits. Geophysical surveys, trench sampling, and XRF ore-grade analysis determine whether a deposit is economic to mine. The ore body chemistry is the single most important determinant of whether a high-purity, low-iron product is achievable — processing can improve but not fundamentally change poor ore chemistry.

Feldspar is predominantly mined by open pit (quarry) methods. After obtaining mining leases (in India, under the Mines and Minerals Development and Regulation Act, MMDR Act, with Environmental Clearance from MoEF), the overburden (soil and weathered rock) is removed by mechanical excavators and bulldozers. The underlying feldspar-rich pegmatite or granite rock is then blasted using controlled explosives or broken using hydraulic rock-breakers for softer formations. Run-of-mine (ROM) ore is loaded into dump trucks and transported to the primary crushing station. Key mining quality controls: selective mining to avoid mixing high-iron zones into the premium ore stream; visual and XRF spot-checking of ROM ore at the mine face; separate stockpiling of different ore grades. India's Rajasthan feldspar operations typically use 10–100 MT/day small-to-medium scale quarries, with leading suppliers consolidating multiple quarry leases for supply consistency.

ROM ore (lump size 200–800 mm) is fed into a jaw crusher, which reduces lump ore to 20–50 mm product through compressive crushing between a fixed and moving jaw plate. Jaw crushers at feldspar processing plants are typically 250×400 mm to 600×900 mm jaw opening size, producing 5–80 MT/hour depending on machine size. Key process parameters: closed-side setting (CSS) controls product top size; liner wear rate affects final product contamination (manganese steel liners contribute negligible iron at normal wear rates). After jaw crushing, material passes over a vibrating scalping screen to remove undersize fines (which may carry excess iron from weathered zones) before secondary crushing. Water sprays at the crushing stage reduce dust and cool the equipment.

Primary crushed material (20–50 mm) is further reduced by a cone crusher (for harder granite-hosted feldspar) or hammer/impact crusher (for softer pegmatite-hosted feldspar) to 5–15 mm. Cone crushers produce more cubical, less angular particles — this matters for downstream sorting and grinding behaviour. Impact crushers produce more angular particles but can cause higher fines generation. The choice depends on ore hardness and deposit type. After secondary crushing, the material is screened to remove material below 1–2 mm (excess fines are diverted to a lower-grade stream or rejected). Clean 5–15 mm crushed ore is stockpiled before beneficiation. At this stage, visual inspection of the crushed ore can identify biotite (dark flakes), quartz (clear crystalline), and tourmaline (black columnar crystals) contamination levels.

This is the most technically critical and differentiated stage in feldspar processing. Beneficiation removes iron-bearing and coloured mineral impurities from crushed feldspar to achieve the required Fe₂O₃ specification. Methods used:

Magnetic Separation: The most common and important step. Crushed feldspar is dried to <1% moisture and fed over a high-intensity dry magnetic separator (HIDS) or — for finer material — a high gradient magnetic separator (HGMS). Iron-bearing minerals (magnetite, biotite, hornblende, ilmenite, hematite) are attracted to the magnetic roll/drum and separated from the feldspar stream. Multiple passes (2–3 stage magnetic separation) are typically used for premium low-iron grades. HIDS operating at 0.6–1.5 Tesla effectively removes weakly magnetic biotite and hematite that conventional low-intensity separators miss. This step is responsible for achieving Fe₂O₃ below 0.2% — sometimes below 0.10% — in premium grades. Without effective magnetic separation, achieving white, bright feldspar for ceramic glazes and fine porcelain is impossible.

Froth Flotation (for premium/ultra-low iron grades): Feldspar is slurried in water with conditioning reagents (fatty acid collectors for feldspar, HF or HBF₄ in acid circuits for quartz separation). Mica minerals float selectively with amine collectors at controlled pH. This achieves Fe₂O₃ below 0.05% in the best grades. Used for premium glass and high-voltage porcelain applications. More complex and expensive than magnetic separation alone.

Optical Sorting / Hand Picking: Smaller operations and premium coarse lump production use optical belt sorters or manual hand-picking to remove visibly discoloured or contaminated pieces before grinding.

Beneficiated feldspar crushed material (5–15 mm) must be dried to moisture below 0.3–0.5% before fine grinding in ball mills or Raymond mills. Excess moisture causes ball mill blockages, reduces grinding efficiency, causes powder caking in silos, and leads to bag-clumping in final packaging. Drying is typically carried out in rotary drum dryers (direct-fired with natural gas or diesel) at 150–250°C inlet temperature, 5–15 minute residence time. Coal-fired dryers are used in some lower-cost operations but risk carbon/soot contamination of the product — not acceptable for premium white feldspar. After drying, material is checked for moisture (LOI at 105°C, target <0.3%) before proceeding to grinding.

Fine grinding reduces dried, beneficiated feldspar from 5–15 mm down to the target powder specification (typically 200 mesh, 300 mesh, or 400 mesh for ceramic applications). Two main grinding systems are used:

Ball Mill (most common for bulk production): Steel-lined cylindrical mills (typically 1.5–3.6 m diameter, 3–8 m length) loaded with steel or ceramic grinding media (balls) rotating at 60–80% critical speed. Ball mills can process 5–50+ MT/hour and produce consistent PSD. Liner and media wear adds trace iron to the product — so for ultra-low iron grades, ceramic-lined ball mills with alumina ceramic grinding media are used (at higher capital cost). Periodic sampling and sieve analysis during grinding maintains specification compliance.

Raymond Mill (for smaller volumes and rapid grade changes): Vertical roller mills where grinding rollers press material against a rotating grinding ring. Built-in air classifier separates on-spec fine powder from coarse returns. Raymond mills are more energy-efficient at fine cuts (200–325 mesh) but have lower throughput than ball mills. Better for custom grades and quick grade changes. Less prone to iron contamination from wear.

For ultra-fine grinding (500 mesh to 2 micron): Attritor mills or jet mills are used for specialty ceramic applications. Much higher energy cost per tonne.

Ground feldspar powder passes through a dynamic air classifier (for ball mill circuits) or integral classifier (in Raymond mill circuits) that separates fine on-spec particles from coarser reject particles returned to the mill for regrinding. The classifier's vane speed, air volume, and feed rate are controlled to achieve the target D50, D90, and mesh pass specification. For standard 200-mesh feldspar, a classifier set to produce D90 < 75 microns is typically used. Key measurement: percentage passing 200-mesh sieve (target ≥95–99% passing for different grades). Product is collected in a bag filter or cyclone system downstream of the classifier and conveyed pneumatically or by screw conveyor to storage silos or packaging. Periodic sieve analysis (every 1–2 hours in production) verifies classifier performance and catches drift before off-spec material is packaged.

A best-in-class feldspar producer maintains quality control at three stages: (1) In-process QC — sieve analysis and moisture checks every 1–2 hours during production; (2) Finished lot QC — full specification analysis per production lot before packaging; (3) Outgoing batch QC — final check before loading for dispatch. Full specification analysis includes: XRF chemical analysis (SiO₂, Al₂O₃, K₂O, Na₂O, Fe₂O₃, TiO₂, CaO, MgO, LOI); particle size distribution (sieve analysis and/or laser diffraction); whiteness/brightness (ISO 2470); pH (5% slurry); bulk density; moisture (LOI at 105°C). A Certificate of Analysis (COA) is issued per batch/lot and accompanies every export shipment.

Finished feldspar powder is packaged in moisture-proof bags: standard 25 kg or 50 kg PP woven bags with polyethylene inner liner, or 500–1000 kg FIBC jumbo bags for bulk export shipments. Storage in covered warehouses on dry pallets — feldspar is hygroscopic and will cake if exposed to humidity for extended periods. Export documentation — commercial invoice, packing list, bill of lading, origin certificate, COA, SDS, fumigation certificate — are prepared and attached to the shipment. FOB loading at Mundra (Gujarat), Mumbai, or Chennai ports for most Indian export shipments. Transit time to European ports: 18–25 days; to Middle East: 7–12 days; to Southeast Asia: 10–18 days.