The Discovery:

Rossmanite was first obtained at the Hradisko quarry, Rožná, Zdar nad Sazavou, Maehren, Jihomoravský Kraj, Moravia, Czech Republic. This the same quarry from where lepidolite mica was first described. The fact that this was a new species of tourmaline was not initially recognized.

The type sample consists of two pink crystals in lepidolite mica. It occurs with with quartz, feldspars, micas, amblygonite-montebrasite, cassiterite, apatite, topaz, beryl, Mn-columbite and other minerals of the tourmaline group. As part of a broad study of the composition of tourmaline group minerals, a small portion of a crystal was sampled from a museum collection sample.

Members of the discovery team [from left to right: Milan Novák, Frank Hawthorne, Julie Selway] and George Rossman standing at the city sign (1997).

After characterization, a formal proposal for a new mineral species was sent to the International Mineralogical Association. The proposal was number IMA1996-018.

Announcement and Publication:

A paper describing an un-named tourmaline with X-site vacancies from the Hradisko pegmatite was presented by Selway et al. in 1995. The formal announcement of the new species was at the Tourmaline 1997 conference held at Nové Mesto na Morave, Czech Republic. The formal publication of the new mineral was by Selway et al. (1998) in American Mineralogist. The mineral species name has been approved by the International Mineralogical Association's committee on new mineral names

The type sample can now be viewed at the Moravian Museum Brno, Czech Republic, in the front row of a case of minerals. It is the sample in the bottom front row, second from the right side.

Composition:

Its ideal chemical formula is X([]) Y(LiAl2) ZAl6 (BO3)3 [Si6O18] (OH)3 (OH) where [] represents a cation vacancy in the X-site. There are three recognized members of the Li-Al tourmalines:

Rossmanite: X([]0) Y(LiAl2) ZAl6 (BO3)3 [Si6O18] (OH)3 (OH)

Elbaite: X(Na+) Y(Li1.5Al1.5) ZAl6 (BO3)3 [Si6O18] (OH)3 (OH)

Liddicoatite: X(Ca2+) Y(Li2Al) ZAl6 (BO3)3 [Si6O18] (OH)3 (OH)

Note that the ratio of Li+ to Al3+ changes to accomodate the charge in the X-site that varies from 0 in rossmanite to 2+ in liddicoatite.

These compositional relationships are often presented on a triangular diagram that represents the composition of the X-site in terms of formula proportions of each component in the X-site. To be rossmanite, a composition must fall in the upper third of the triangular diagram (with the other necessary components in the other sites as well). The red dots illustrate three compositions that fall within this field.

 

Structure

The atomic structure of the mineral, as reported in Selway et al (1998) is available from the American Mineralogist Crystal Structure Database.

Here are three views of the structure:

1) looking down the c-axis

2) looking up the c-axis

3) looking almost perpendicular to the c-axis


Related Hypothetical Minerals:

A hypothetical tourmaline composition is X([]) Y(LiAl2) ZAl6 (BO3)3 [Si6O18] (OH)3 (F). Here, F replaces OH in one site.

This hypothetical composition has been called "fluor-rossmanite". Although this name is not formally recognized as a mineral, a composition that falls in this field has been reported in an Omapyo, Namibia tourmaline.

Another hypothetical tourmaline composition is X([]) Y(Li0.5Al2.5) ZAl6 (BO3)3 [Si6O18] (OH)3 (O). Here, O replaces OH in one site.

This hypothetical composition has been called "oxy-rossmanite". Although this name is not formally recognized as a mineral, a composition that falls in this field has been reported in an Eibenstein an der Thaya, Austria, tourmaline.


References:

Selway GJB, Novák M, Hawthorne FC, Cerný P (1995) Aluminous X-site vacant tourmaline from the Hradisko pegmatite, Czech Republic. Abstracts, GAC/MAC meeting, Winnipeg 1996.

Selway GJB, Novák M, Hawthorne FC, Cerný P, Ottolini L, Kyser TK (1998) Rossmanite [](LiAl2)Al6(Si6O18)(BO3)3(OH)4, a new alkali deficient tourmaline: description and crystal structure. American Mineralogist, 83(7-8):896–900.

last updated: 2Nov-2012



Return to the main page:

http://minerals.gps.caltech.edu/rossmanite/Index.html