## 5 Conclusions  
The base of the laterite weathering profile is mainly serpentinites probably formed from harzburgites. Locally, almost non-serpentinized harzburgite was found in the basement.  
In the studied deposit zone, oxide ore was found to be dominant over saprolite ore, which allows classifying this deposit as a mixed oxide-saprolite type.  
The main mineral in the limonite horizon is goethite prevailing over hematite, which significantly distinguishes the Halmahera deposits from other lateritic deposits of Indonesia.  
In the limonite horizon the deposit minerals are: Ni-goethite, asbolane, and other manganese minerals. In the saprolite horizon, the deposit minerals are mainlyathered primary lysardite and chrysotile. These minerals are enriched in Ni, which probably migrated with solutions from the limonite horizon. The enrichment in Ni is both residual (typically in the upper part of the limonite horizon) and supergene (in the lower part of the limonite horizon and in the transition and saprolite horizons).  
The formation of the deposit is probably related to the disintegration of primary minerals, i.e., minerals from the serpentine group and magnesium silicates building harzburgites. In both cases the disintegration led to the formation of ferruginous weathering with a dominant share of goethite.  
In the deposit profile, goethite from the lower part contains more Ni than goethite from the upper part. Furthermore, the goethite in the lower part of the profile was found to be weakly crystalline and the average crystal size was larger in the upper part. This can probably be related to the transformation and recrystallization processes resulting in the release of Ni\({}^{2+}\) into solutions.  
Garnierites were found in the deposit profile and occur depending on the degree of serpentinization of the underlying rock. Garnierites occur only where the degree of serpentinization of harzburgite is low and appear in zones of loosening and voids. Garnierites are composed of two types of minerals: minerals belonging to the lysardite-repouite series and minerals belonging to the kerolite-pimelite series.  
Figure 15: Summary of Ni concentration data for 117 global laterite Ni deposits with plotted Ni concentration results for Block B of the Central Halmahera deposit at several selected cut-off criteria. On the basis of [4] modified. Intercepts for the 90 th, 50 th, and 10 th percentiles of the observed distribution are provided.  
Local occurrence of very good quality saprolite ore (2-3% Ni) was found in the deposit. However, low quality limonite ore (approximately 1% Ni) dominates in terms of quantity and its extraction under the present conditions is economically unprofitable.  
Conceptualization, G.K. and K.S.; methodology, G.K.; software, G.K.; validation, G.K.; formal analysis, G.K.; investigation, G.K., K.S. and K.Z.; resources, G.K.; data curation, G.K.; writing--original draft preparation, G.K.; writing--review and editing, K.S. and K.Z.; visualization, G.K. and K.Z.; supervision, K.S. and K.Z.; project administration, K.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Halmahera Percasa Ltd. Djakarta, Indonesia: 001-HPL.  
The authors express their thanks to [PERSON], president of Halmahera Resources Percasa Ltd. for funding the field research and part of the analytical studies.  
The authors declare no conflict of interest.