deposits
A point on a deposit map is not the deposit. It is a position somebody placed, at a precision they wrote down, inside a zone that may be kilometres across — and the file it arrives in will happily give you thirteen decimal places.
About: Bingham Canyon
The compilers of the sediment-hosted zinc-lead database say exactly what their coordinates are. All locations were checked against satellite imagery; many differ substantially from previously published positions as a result; and a location "is intended to plot within the alteration zone of deposit which may be kilometers across". It is a point inside a zone, not the centre of one and not a shaft.[1]
Lithoen therefore stores these as representative points with approximate boundary certainty, and draws no polygon around any of them. Where only a point exists, only a point is published: a shape invented around a coordinate would be a claim about extent that nobody made.[1]
The decimal-degree columns of the porphyry database carry up to fifteen decimal places. A tenth of a micrometre. Those digits are floating-point residue from the degrees, minutes and seconds the compilers actually wrote: 355 of the 690 rows have no seconds at all and were authored to the nearest minute, about 1.85 kilometres, and some to the whole degree.[1]
Publishing the stored digits would assert a position about a billion times better known than the one anybody determined. Lithoen rounds each point to the coarser of its two axes and records the authored precision on the record, where a validator checks it. Chuquicamata lands at two decimal places because its longitude was written to the minute even though its latitude has seconds; Oyu Tolgoi lands at two because its latitude is a whole degree.[1]
Thirteen of the deposits in this corpus carry no position. The chromite, laterite and volcanogenic massive sulfide models locate their examples by naming a region and by figures at continental scale, and neither accepted database covers those classes. Each of those records says so in a claim rather than leaving the page quiet.[1]
The alternative would have been to look the name up somewhere and write down what came back. A coordinate obtained that way is indistinguishable, on the page and in the data, from one a compiler placed against imagery — which is precisely why it must not be done.[1]
Often said
“More decimal places means a better-known position.”
What the evidence supports
The porphyry database stores up to fifteen and authored, in most rows, three: degrees and minutes. The extra digits are unit-conversion residue.
Supporting records: deposit-coordinate-precision
Often said
“A deposit marker shows where the deposit is.”
What the evidence supports
It shows a point the compilers placed somewhere inside a zone that may be kilometres across. The deposit is bigger than the dot and not centred on it.
Supporting records: deposit-coordinate-is-a-point-in-a-zone
Bracketed references link to the structured entity records whose claims support each paragraph. Last updated 2026-09-07.