The main subject of research in this paper is glauconite with its useful parameters, which is the object of exploitation in the “Górka Lubartowska-Niedźwiada” deposit. The main glauconitic horizon (lower Eocene) is built by loamy fine-grained and medium greenish sands with marine fauna and fragments of amber (ca. 7 m thick). Thin lamins and pockets of silts containing phosphorites and also glauconitic sands with underlaying very thin quartz-glauconitic sands are found at the bottom of this layer. The glauconite deposit in “Górka Lubartowska-Niedźwiada” is an amount of ca. 30% by volume of the main glauconitic horizon. Glauconite of the 1M polytype (XRD) shows large granulometric and morphological differentiation (SEM-EDS). It frequently contains aggregations of euhedral or framboidal pyrite grains (RS), which is indicative of the euxinic nature of the formation environment of the rocks under study. The individual glauconite grains show distinct chemical variability, manifested in a lower share of Al2O3 and an increased content of MgO and CaO (EPMA, XRF). At the same time, a large share of K2O (above 8% by weight) allows it to be included in highly matured glauconite, thus it can be considered as a potential raw material for the production of mineral fertilizers. The association of glauconite with phosphates (SEM-EDS) and anatase inclusions in the grains of glauconite (RS) indirectly point to the contribution of the decomposing organic matter to the formation of grains of this mineral. The xylite fragments preserved in the sediment show a low degree of coalification, which is typical of soft lignite. This also shows that the transformation process was taking place under a relatively small overburden.

The Sin Quyen deposit is characterized by a high accumulation of rare earth elements (REE). This deposit belongs to the IOCG type copper deposits (Iron Oxide Copper-Gold Deposits). In the deposit, the REE carrier minerals have been identified as follow: allanite, titanite, uraninite, monazite, apatite, chevkinite, aeschynite, bastnäsite, and epidote. In the skarn zone, contents of allanite range from single percentages to 10% in hand-size specimens. Locally, minerals of epidote subgroup which occur in large amounts in the host rocks are important. The studied allanites have concentrations of: REE (14–27 wt%), Ca (9–16 wt%), Al (8–19 wt%), Si (26–34 wt%) and Fe (12–21 wt%). Two populations of allanite are documented, the first is texturally older and probably related to the Ca-K alteration (second stage of crystallization). This population has higher REE concentration ranging from 20 to 27 wt%. The second population is texturally younger and has a lower total REE concentration ranging from 14 to 19.9 wt%, which occur mostly as a rim surrounding the older and likely arose during the K alteration with Cu-Au mineralization (third crystallization). The chemical composition indicates that the studied allanites belong to the Ce-La-ferriallanite family, with low ΣHREE and an average of 0.21 wt.%. A temperature of 355°C which was calculated using a value of δ34S isotopes is interpreted as a temperature of the second crystallization stage of allanite. In the studied deposit, excluding allanite and titanite, the other bearing REE minerals have an insignificant role in the REE balance, since they either have the total content of REE, which is often close to the WDS detection limit (rf. the epidote subgroup), or their only occur at the single points. The content of total REE in accessory uraninites is high and range from 1.311% up to 7.959% with an average value of 4.852%.