1907
Establishment of the company; mining of Rhine slate in up to 6 underground mines in the region of Bundenbach.
1970
Theis-Böger was the first german company which started importing significant amounts of slate from Spain. This imported slate became soon very popular among architects, roof tilers and building contractors under the protected trademark Assulo®.
1984
Re-opening of the traditional and significant Altlay mine in the Rhenish mountains. Altlay is among the best slate-mining areas in Germany.
1988
Establishment of the spanish subsidiary Theboe S.A. Own production of all sizes, quality control and assurance in the country of origin of Assulo® slate.
Today
Slate mining at the Altlay site now takes place underground and is thus environmentally compatible. Currently this valuable product is being mined at a depth of approximately 120 meters. The most modern technology is used, as developed in-house in accordance with individual requirements. Theis-Böger's production range has been expanded with new grades from mining sites worldwide, such as Monte Color®.
