Is brookite magnetic?
Mostly not: USGS left most of 2 brookite samples behind at 1.70 amp but pulled a tail from 0.70. 25 of 377 rows in its table show that pattern; 13 start lower.
Mostly not. USGS Open-File Report 99-529 ran 2 brookite samples through a Frantz separator: most of each stayed behind at 1.70 amp, the maximum, but a fraction was pulled from 0.70 amp upward. The Handbook sheet for brookite, TiO2, hardness 5.5 to 6, prints no magnetic property. Of the table’s 377 rows, 25 show that mostly-not, small-tail pattern.
In short
- Two sources, one row. USGS Open-File Report 99-529 (Rosenblum and Brownfield) gives brookite a total range of 0.70 to above 1.70 amp and a best range above 1.70, on 2 samples. The report calls diamagnetic the minerals that are nonmagnetic at 1.70 amps and paramagnetic those separable up to 1.70. The Handbook of Mineralogy brookite sheet prints no magnetic property.
- The tail shelf. A script over all 377 data rows of USGS Open-File Report 99-529, Table 1 finds 25 rows like brookite’s: best range above 1.70, so most of the sample stayed behind, but a total range that starts lower, so a fraction came out. Brookite and tennantite start at 0.70 amp; 13 rows start lower, down to 0.30, and 10 start higher, up to 1.40. Rutile is on the shelf at 0.80; anatase is not.
- Documented failure: the contamination sentence. USGS writes that for samples showing a range from 0.50 or 1.00 amps to above 1.70, probably some contamination was involved, though often it could not be sure even under the microscope. 12 of the 25 tail rows start at exactly 0.50 or 1.00; brookite’s 0.70 is not one of the two figures, and the report says nothing about it. This page does not assign the tail a cause.
- Brookite’s company on the separator. The sheet’s Association line names anatase, rutile, titanite, orthoclase, quartz, hematite, calcite, chlorite and muscovite. In Table 1, hematite’s best range is 0.10 to 0.30 amp and chlorite’s 0.20 to 0.50; anatase, quartz, calcite and orthoclase were never pulled. A pull at low current points to the company.
- The decision. Brookite is not a magnet mineral on any record here: no sheet wording, and a separator row where most of each sample stayed behind. Anatase’s single sample is on is anatase magnetic; the split between ilmenite and the TiO2 rows is on is ilmenite magnetic. The species facts are on brookite.
| Total range starts at | Rows | Table 1 names | Named in USGS’s contamination sentence? |
|---|---|---|---|
| 0.30 amp | 3 | Clinosafflorite, Mansfieldite, Metacinnabar | No |
| 0.40 amp | 1 | Hewittite | No |
| 0.50 amp | 9 | Colusite, Graphite, Liebigite, Microlite, Oligoclase, Patronite, Skutterudite-(Ni), Tetrahedrite-(Ag), Turquoise | Yes |
| 0.70 amp | 2 | Brookite (2 samples), Tennantite | No |
| 0.80 amp | 2 | Covellite, Rutile (10 samples) | No |
| 0.90 amp | 1 | Fluorite | No |
| 1.00 amp | 3 | Arsenopyrite, Digenite, Hauyne | Yes |
| 1.10 to 1.40 amp | 4 | Metatorbernite (1.10), Hexagonite (1.20), Sphalerite (1.30), Apatite (1.40) | No |
| All tail rows | 25 of 377 | None flagged often-locked or depends-on-chemistry | 12 yes, 13 no |
Is brookite magnetic? What USGS measured
USGS pulled part of its brookite at 0.70 amp and left most of it behind at 1.70. USGS Open-File Report 99-529 (Rosenblum and Brownfield) ran 1084 samples of 378 mineral species through Frantz isodynamic separators, on grains of 125 to 150 micrometres at a 15° side tilt. Brookite’s row: total range 0.70 to above 1.70 amp, best range above 1.70, 2 samples, with no often-locked flag and no depends-on-chemistry note. The report defines diamagnetic minerals as nonmagnetic at 1.70 amps, paramagnetic as separable up to 1.70, and ferromagnetic as strongly attracted to a magnet, like a piece of iron.
Reading the two ranges. The best range is where most of the sample came out; above 1.70 means most stayed behind at the separator’s greatest current. The total range is everything that came out at any setting; starting at 0.70 means some grains moved from there upward. So brookite sits on neither side cleanly: most of it nonmagnetic at 1.70 amps, the report’s diamagnetic, with a fraction of unstated size that was separable from 0.70 amp. The report is concerned with practical separation, not with susceptibility in physical units.
What the sheet says. The Handbook of Mineralogy brookite sheet prints no magnetic property. Its two analyses, from Snowdon, Wales, and Magnet Cove, Arkansas, carry 1.41 and 1.48 wt% Fe2O3, about 1% iron by mass; those are the sheet’s samples, not USGS’s, so they cannot explain the row. Magnet Cove is a place name, and the sheet does not explain it. The site-wide summary is on which minerals are magnetic.
How common is a tail like brookite’s? The tail shelf
25 of 377 rows share brookite’s pattern, and brookite’s tail starts in the middle of them. Method: a script parsed every data line of Table 1 into name, total range, best range and sample count, kept the rows whose total range is written from a start below 1.70 to above 1.70, and of those kept the ones whose best range is written exactly above 1.70. Result: 56 rows run from a lower start to above 1.70; 25 of them have their best range above 1.70. Brookite and tennantite start at 0.70; 13 rows start lower and 10 higher.
Sample counts. 12 of the 25 rest on 1 sample and 5, brookite among them, on 2; rutile, with 10, is the best-sampled. None of the 25 carries the often-locked flag or the depends-on-chemistry note. The report says its data rest on 1 to 18 samples per species and that more samples give better reliability; two brookite samples are a result, not a range of behaviour.
Not the same as the other pages. The never-pulled, one-sample rows are counted on is anatase magnetic; the titanium minerals in order of best range are on is ilmenite magnetic, which also gives brookite’s 0.70 start. Neither asset is repeated here: this page counts the rows with a tail.
Why did some brookite pull? The contamination sentence
USGS does not say, and neither does this page. The report writes that for samples that showed a range from 0.50 or 1.00 amps to above 1.70, probably some contamination was involved, and that often this cannot be confirmed even after microscopic examination, so the whole range is reported. It also writes that micro-inclusions of magnetite or other ferromagnetic minerals make the lower limit of extraction difficult or impossible to determine, and that chemistry is the main factor controlling magnetic susceptibility.
Documented failure: 0.70 is not in the sentence. Of the 25 tail rows, 12 start at exactly 0.50 or 1.00 amp, the two figures the sentence names; 13, brookite and rutile among them, start elsewhere. The report does not say whether it meant the sentence to cover them. Reading brookite’s tail as contamination would put words in USGS’s mouth; reading it as brookite’s own magnetism would too.
The other TiO2 rows. Anatase’s 1 sample was never pulled; rutile’s 10 samples have a total range of 0.80 to above 1.70 and a best range above 1.70, one step behind brookite on the same shelf. All three are TiO2, and the separations that do work between the three are on anatase vs rutile and brookite.
What if a brookite specimen sticks to a magnet?
Look at the company before the brookite. Neither source tests a hand magnet, so this is a reading of the records, not a test result. The brookite sheet’s Association line names anatase, rutile, titanite, orthoclase, quartz, hematite, calcite, chlorite and muscovite. In Table 1, hematite (11 samples, often locked) has a best range of 0.10 to 0.30 amp; chlorite (9) 0.20 to 0.50; muscovite (9) 0.70 to 1.30, depends on chemistry; titanite (4) 0.80 to above 1.70, depends on chemistry; anatase, quartz, calcite and orthoclase were never pulled.
What to check instead. Brookite is the tabular or pyramidal TiO2, hardness 5.5 to 6, with a white to yellowish white streak; a 20.00 g piece reads 15.10 to 15.22 g in water. The weighing method is on how to measure specific gravity at home.
On the label. Write brookite when habit, streak and weight agree, whatever the magnet does. The magnetism questions are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.