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GeneralNumber & Diversity of Mineral Species - R. Hazen

24th Jan 2015 21:02 UTCKelly Nash 🌟 Expert

The latest issue of Mineralogical Record includes a DVD from the Dallas Mineral Collecting Symposium last August. The first talk, by Dr. Robert Hazen, was the best presentation on minerals I’ve seen. Towards the end, he references unpublished work by Grethe Hystad, (U of Arizona) and others, on the diversity of minerals on earth. They used distributions of species at localities in Mindat to extrapolate how many minerals exist on earth (using current analytical capabilities): the number is 6,437. If so, about 1,500 more minerals are due to be discovered (again, pending new methods that look at tinier specimens). Also, using statistical methodology, and with 15-20 thousand "plausible" minerals, it was possible to calculate the number of species that would show up at random if history was “replayed” – and the number is about 1,000. So, nearly a quarter of the known species make a mineral assemblage that is unique to earth. A very interesting exercise, and one which points out the value of the Mindat locality database.

24th Jan 2015 23:47 UTCMatthew Stanley

I just finished watching this too. Very good presentation. It got me wondering, is it possible to sort the species on mindat by the number of localities at which they are found in order to replicate Grethe's findings?

25th Jan 2015 10:38 UTCDavid Von Bargen Manager

" It got me wondering, is it possible to sort the species on mindat by the number of localities at which they are found in order to replicate Grethe's findings?" - The query to generate this takes a bit of time so it is only available to managers. The top 50 species are listed below.

50 Chrysocolla 3304

49 Chromite 3346

48 Copper 3444

47 Diopside 3510

46 Beryl 3657

45 Covellite 3716

44 Titanite 4316

43 Kaolinite 4343

42 Microcline 4412

41 Ilmenite 4447

40 Zircon 4455

39 Scheelite 4576

38 Marcasite 4615

37 Cerussite 4703

36 Rutile 4795

35 Cassiterite 4807

34 Silver 4808

33 Tourmaline 4836

32 Tetrahedrite 4963

31 Azurite 5114

30 Bornite 5134

29 Chalcocite 5278

28 Molybdenite 5450

27 Apatite 5495

26 Garnet 5648

25 Siderite 5822

24 Gypsum 5841

23 Sericite 5954

22 Goethite 6527

21 Albite 6787

20 Dolomite 7365

19 Epidote 7397

18 Biotite 7544

17 Pyrrhotite 8040

16 Arsenopyrite 8049

15 Muscovite 9023

14 Fluorite 9208

13 Chlorite Group 10109

12 Baryte 10675

11 Limonite 10787

10 Malachite 11229

9 Hematite 12349

8 Magnetite 13184

7 Sphalerite 19573

6 Galena 21840

5 Calcite 24664

4 Chalcopyrite 24754

3 Gold 24863

2 Pyrite 35193

1 Quartz 48941

25th Jan 2015 13:50 UTCReiner Mielke Expert

Any such list would be heavily biased and you would somehow have to filter that out to yield any sort of meaningful data. For example the number of localities for gold is disproportionally high compared to biotite simply because it is of more interest to people. Also how do you account for the redefinition of species, for example biotite which is no longer a valid mineral species but a group of species. Probably the best way to determine the potential is to simply look at the number of discoveries over time while comparing it to available technology and then extrapolating that.

25th Jan 2015 14:18 UTCJolyon Ralph Founder

The other issue with Gold is that we did an automated script to add mines from MRDS to the database, and tried to import mineral species where known. With a 'copper' or 'iron' mine without further information we can't guess at the species, but with a 'gold mine' we can. It is a bit misleading and does distort this particular statistic tremendously.

25th Jan 2015 18:24 UTCLászló Horváth Manager

If sericite is so high on this list I wonder how many collectors have or care to admit having specimens of sericite. Ditto kaolinite.

Another interesting exercise might be. If you would remove these 50 species from the show in Tucson what would be left?

25th Jan 2015 18:50 UTCAlfredo Petrov Manager

If an extraterrestrial geologist could afford only a very brief stop on Earth, and that stop was in Tucson in early February, he would conclude that Earth was largely composed of pegmatites and copper-bearing gossan.

25th Jan 2015 19:07 UTCChester S. Lemanski, Jr.

Jolyon,

The gold issue is not necessarily that biased. The MRDS files may designate a mine as a Au mine or list Au among other commodities; however, unless the file specifically lists Au as a mineral, it was not carried over to Mindat from MRDS as a species listing. If such MRDS files that do not list Au as a species include other data indicating actual visible Au occurring in a mine (e.g., a comment under the geology description stating "coarse gold" or "free-milling gold"), then I will add it; otherwise, not. There are instances where MRDS lists Au as species but the other data in the file do not support the occurrence of visible Au. In such cases I may delete the gold entry from the Mindat file. Similarly, many placer deposits/mines listed in MRDS did not list Au as a species. Many of these can be interpreted as being a valid Au occurrence since there was production documented, or, again, comments clearly indicating the occurrence of visible Au (e.g., "fine material" or "coarse nuggets"). Lacking such indications of placer Au I do not add it as a species for such locations. The really vague localities never have the Au added as a species. Essentially they are only "reported" or otherwise unconfirmed occurrences, and I often use that word as a qualifier without listing Au as occurring there. If it is already listed in such a file, I will probably delete it in the very small number of cases where that might be the case. This is particularly to my ongoing California project since that state has more Au occurrences documented than anywhere else. It also applied to Arizona files. Future projects for Nevada, Utah, New Mexico, Oregon, Washington, Idaho, etc. will require the same discrimination when dealing with the MRDS data. By the way, these same criteria apply to Pt/PGE group occurrences. It is also necessary to clarify these Au occurrence by adding the appropriate wording (e.g. "placer material" or "free-milling fine gold," etc.) in the remarks or description data field on the mineral edit page for the species at the locality.

Sericite is so common because it is often listed in the USGS MRDS files as a specific alteration product in or around veins and deposits, i.e. "sericitization." Ditto with kaolinite.

Chet

25th Jan 2015 22:27 UTCKelly Nash 🌟 Expert

If you watch the talk, Hazen says the diversity of species is really determined by the rare minerals, not the common ones. The 50 most common are not that important to the statistical method - more than half of known minerals are known from 5 localities or less so that is more than half of the curve that is used to predict diversity.

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