**Mineralogical and Chemical Characterization of Zr-REE-Nb Ores from Khalzan Buregtei (Mongolia)—Approaches to More E** ffi**cient Extraction of Rare Metals from Alkaline Granitoids**

**Lars Hans Gronen 1,\*, Sven Sindern 1, Janet Lucja Katzmarzyk 2, Udo Bormann 1, André Hellmann 1, Hermann Wotruba 2 and F. Michael Meyer 1,3**


Received: 11 February 2019; Accepted: 3 April 2019; Published: 5 April 2019

**Abstract:** Alkaline rocks are worldwide observed as hosts for rare metal (Zr-REE-Nb) minerals. The classification of the ore bearing rock type is challenging due to the fact that textures and mineral assemblage are obscured by post-magmatic alteration. In addition, the alteration causes fine and intricate intergrowth of the ore minerals with associated gangue. Hence, intensive comminution is necessary to liberate the ore minerals, which is one parameter hampering the economical use of this deposit type. This study provides a quantitative mineralogical investigation of the ore bearing rock suite at Khalzan Buregtei as an example of rare metal deposits. R1-R2 multication parameters are shown to be highly appropriate as quantitative mineralogical indicators based on readily available major element datasets to visualize and quantify alteration types of the ore bearing rock suite. The ore minerals were found to be associated with a cluster-forming assemblage of post-magmatic phases. Automated mineralogy was applied to quantify the textural properties of the ore mineral clusters. This finding permits e fficient pre-concentration of rare metal ore at coarser particle size fraction, requiring less energy consuming comminution.

**Keywords:** Zr-REE-Nb deposits; alkaline rocks; automated mineralogy; Khalzan Buregtei
