What primary source supports the Hall-Héroult era aluminium price figures ($16/lb 1884 → $2/lb 1889 → $0.5/lb 1894)?

claim-aluminium-price-fell-monotonically-after-hall-heroult rests on Wikipedia's "History of aluminium" article for a specific, load-bearing quantitative sequence: roughly $16/lb in 1884, falling to $2/lb in 1889 and $0.5/lb in 1894. Wikipedia is Tier 4 — fine for locating the claim, not for resting a quantitative claim as verified, especially since this figure is doing real work: it's the empirical counterexample to a vault model prediction (claim-asteroid-pgm-price-holds-then-collapses) and the anchor for claim-cheaper-extraction-disruptions-fall-monotonically-not-hold-then-collapse.

What's needed: a Tier 1–2 source carrying the same or comparable price series — candidates: contemporary trade-press price quotations (e.g. Engineering and Mining Journal archives), USGS historical aluminium price/production statistics, the Aluminum Association's historical data, Alcoa company records, or an economic-history paper on the Hall-Héroult price collapse (there is a well-known literature on this as a textbook case of a technology-driven price collapse).

Candidate next moves:

• Check USGS Mineral Commodity Summaries historical series for aluminium (they often carry price data back to the 1880s).
• Search for the specific $16 → $2 → $0.50 figures in an economic-history source to confirm Wikipedia didn't garble a decimal or a currency-year adjustment.
• If a primary confirms the monotonic shape (no plateau), promote claim-aluminium-price-fell-monotonically-after-hall-heroult out of [unverified-quant] and consider upgrading its source_tier.

Progress log

• 2026-07-22: Answered by claim-wikipedia-aluminium-price-sequence-is-a-citation-splice, claim-usgs-lacks-aluminium-price-data-1884-1894, claim-richards-1896-preface-gives-different-aluminium-price-figures, and claim-skrabec-lockwood-disagree-on-1884-aluminium-silver-price. What settled it: an exhaustive chase down the citation chain found no single primary source supports the full sequence as commonly quoted — Wikipedia splices two unrelated secondary authors (Skrabec for 1884, Hanners for 1889/1894); the USGS's own compiled price series has no data at all for 1884, 1889, or 1894; and the one genuine primary reached (Richards' own 1896 preface) gives a different, if directionally consistent, pair of numbers ($12/lb ~1885, $0.50/lb late 1895). The question as raised — 'is there a Tier 1-2 source for this exact sequence' — is answered in the negative, definitively, not left open for want of trying. The narrower residual thread (whether Richards' own internal Statistics section matches Hanners' paraphrase) is a distinct, more specific question, routed separately to question-richards-1896-statistics-section-price-table.