Batugamping berwarna merah yang tersebar secara setempat-setempat dan berasosiasi dengan batugamping berwarna putih hingga abuabu yang dijumpai di Daerah Ponjong, Kabupaten Gunungkidul, Daerah Istimewa Yogyakarta, termasuk dalam Formasi Wonosari-Punung. Batugamping tersebut perlu diteliti karakteristik mineralogi dan geokimianya, yang sangat diperlukan dalam memahami genesa batugamping di daerah tersebut. Pengamatan petrografi dan XRD pada batugamping merah menunjukkan hadirnya mineral kalsit, kuarsa, siderit, hematit, dan titanit. Analisis geokimia oksida mayor batugamping merah memperlihatkan tren pengkayaan senyawa SiO2, TiO2, Fe2O3 dan MnO yang diinterpretasikan berhubungan dengan kehadiran mineral-mineral titanit (CaTiSiO5), siderit (FeCO3), hematit (Fe2O3), dan diduga rodokrosit (MnCO3). Mineral-mineral tersebut mempunyai karakteristik warna coklat kekuningan, merah muda sampai merah sehingga dimungkinkan dapat memberikan warna merah pada batugamping. Ada tiga proses yang diinterpretasi berperan dalam genesa batugamping merah Ponjong yaitu pengaruh material terigenus yang mengandung oksida SiO 2 , Al 2 O 3 , Fe 2 O 3 , dan TiO2 saat pengendapan batugamping, proses diagenesis oleh air meterorik yang mengkayakan senyawa Fe2O3 dan proses bekerjanya larutan hidrotermal.

Isolation of ureolytic bacteria and geochemical analysis of beachrock from Krakal-Sadranan Beach (Yogyakarta, Indonesia) were conducted to determine natural sedimentary characteristics of the beachrock. The beachrock was also examined to determine the depositional conditions and distribution of rare earth elements. An increased concentration of total rare earth elements, both heavy rare earth elements (terbium, dysprosium, yttrium, holmium, erbium, thulium, ytterbium, and lutetium) and light rare earth elements (lanthanum, cesium, praseodymium, neodymium, samarium, europium, and gadolinium) signals that the beachrock deposition process happened under oxidative environmental conditions. This study proposes the novel use of ureolytic bacteria in a depositional environment for carbonate control of a sedimentary process for the development of artificial rock to mitigate coastal erosion. The resulting bacterial strains are highly homologous to the 16S rDNA nucleotide sequence of the species Oceanobacillus profundus, Vibrio maritimus, and Pseudoalteromonas tetradonis.

Beachrock is among the important features of tropical coastlines. It appears to have an anchoring effect on dynamic islands that provides protection from erosion. However, the origin of cement micritic peloidal remains uncertain. Petrographic analysis is a method used by many geologists to accurately identify specific aggregated minerals present in an area. It also helps to understand historical petrogenesis interpretations of a sedimentary rock formation and cementation process inside rock particles. In this study, petrographic analysis was used to identify the structure, texture, composition, and presence of minerals from beachrock samples collected from Okinawa, Japan and Sadranan beach, Yogyakarta, Indonesia. Field investigations and laboratory analysis (petrographic and geochemical measurements) were aimed at understanding the formation mechanism of natural fresh beachrock. Subsequently, laboratory-scale experiments on artificial beachrock were based on solidification tests and were conducted to use microbial-induced calcium carbonate precipitation (MICP) with Pararodhobacter and Ocenisphaera bacterium species to draw comparisons between natural beachrock and artificial beachrock. The cementation process based on petrographic analysis of thin sections has an assumption that the cement type and other added materials determine the strength of the material, and that the cement mineral occurring represents the sedimentary environment. The cement mechanism behavior of natural beachrock has potential in manufacturing artificial beachrock using the MICP method, an eco-friendly development method for coastal areas.

The eastern slope of Mount Sumbing has many springs used as a source of raw water for hygienic sanitation purposes. However, there has been no scientific research showing the quality of springs. Therefore the purpose of this study is to analyze the quality of springs on the eastern slopes of Mount Sumbing for community sanitation hygiene purposes based on water physical and chemical properties. Water samples were taken from several points in the study area and observed for physical parameters (TDS, smell, taste, and temperature) and chemical parameters (acidity, nitrate, fluoride, and sulfates). The results showed that from 30 samples of springs, only one spring fulfilled the Indonesia Minister of Health Regulation No. 32 in 2017. The spring located at STA 51 Kaliloro, Krajan, Kaliangkrik, Magelang Regency. There was a spring classified as deep geothermal groundwater and the others classified as shallow groundwater. Based on the acidity of water, most of the springs on the eastern slopes of Mount Sumbing could be used as hygiene sanitation by treating the water acidity and regulating the purposes of springs.

A geochemical study was carried out to determine the geochemical characteristics of limestone in Wonosari-Punung Formation, and to suggest its depositional conditions and the source of rare earth elements. The study was conducted at Ponjong Area, Gunungkidul Regency, Daerah Istimewa Yogyakarta, Indonesia. White limestone which contains more abundant calcite is characterized by the highest CaO concentration. Red limestone which is associated with impure minerals such as siderite, rodochrosite, hematite, and titanite is typified by depleted CaO but higher SiO 2 , Fe 2 O 3 , MnO, and TiO 2 concentrations. Grey limestone characterized by depleted CaO and higher MnO contents is considered to be influenced by the presence of impure minerals of manganite (Mn 2 O 3 .H 2 O) and/or pyrolusite (MnO 2). Depletion of Sr concentration in the coloured limestone indicates that the diagenetic process increases from the white limestone to the coloured limestone. The process possibly occurred post-deposition of the limestones. The limestones show positive Mn* values (2.46-2.95) and authigenic U values (0.89-3.38) that suggest an oxidative environment. The Ce/Ce* values (0.57-0.80), Eu/Eu* values (1.04-1.88), high Y/Ho ratio, and low La N /Yb N ratio are indications that the rare earth elements in the limestones were derived from terrigenous materials. The positive Eu anomaly and enrichment of Cr and Mn of the limestones are indications of hydrothermal fluid activity taking place in the studied area. Based on the geochemical characteristics of the Punung-Wonosari limestones, the depositional environment and the source of rare earth elements of the limestones were therefore influenced by a combination of hydrothermal fluid activity with small amount of terrigenous material input and post depositional diagenetic process.

Besole area, Tulungagung regency, East Java province is an area with measured marble resource potential of 15 million tons. This study aims to determine marble recommendations based on their characteristics. Marble characteristic has brownish white-brown description of megascopis, non-foliated structure, based on fracture density measurement using inventory method, marble has medium density, based on petrographic analysis, marble has crystal size ≤ 0.5 - 2 mm, having texture of metamorphism process resistance ie crystalloblastic and relict, texture of mineral form that is granoblastic, texture of metamorphic rock is decussate and saccharoidal. The composition of marble consists of calcite, dolomite and hematite. Based on analysis of geochemical test using method of ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy), marble has the main oxide content dominated by CaO 54.6% - 56%, based on the analysis of engineering test yields the average value of compressive strength test of 781,713 kg / cm², wear resistance value 0.0399 mm / min and water absorption value 0.704%. The recommended use of marble based on solid density is utilized as a residential floor with a size of ≤10-40 cm, based on its geochemistry used as paper industry, textile dye, pesticide production, sugar screening and cement production, and based on its technique is used as floor with live load> 250 kg / cm², inner and outer construction stone, and light - medium construction foundation

The Tumpangpitu high sulfidation (HS) epithermal gold deposit is located in the south coast of East Java, Banyuwangi District, East Java Province, Indonesia. This area lies within the central portion of the Cenozoic Sunda‐Banda magmatic arc which trends southeast from northern Sumatra to west Java then eastward through east Java, Bali, Lombok, Sumbawa and terminating at Banda sea. The geology of the Tumpangpitu is predominantly occupied by Late Oligocene to Middle Miocene low-K calc-alkaline to alkaline andesitic volcanic rocks and interbedded with volcaniclastic rock sequences, which are associated with low-K intermediate intrusions. The mineralization style at the Tumpangpitu area is composed of a high‐sulfidation (HS) epithermal gold-copper system which is typically associated with concealed gold-rich porphyry copper system. The HS epithermal mineralization is hosted by volcanic and volcaniclastic rocks in this research area. The mineralization domains are divided into Zone A, Zone B and Zone C which are situated along NW-SE-trending silica ledges zones. The HS epithermal mineralization is texturally occurs as vuggy replacements mineralization as well as stockworks, disseminated forms, fractures and veins. Fluid inclusion study was conducted for 6 quartz vein samples which petrographically entrapped fluid inclusions. Homogenization temperature (Th) and melting temperature (Tm) can microthermometrically be determined by fluid inclusion analysis. The average homogenization temperature (Th) of the fluid inclusions gives 180˚C to 342˚C and melting temperature are from -0.1 ˚C to -1.4˚C. Tm corresponds to the salinities ranging from 0.1 to 4.5 wt% NaCl equivalent. The paleodepth of ore formation can be estimated from the salinity of fluid. Since the deposit was not formed at boiling condition, the minimum paleodepth of ore (quartz) samples taken from both shallow level (53.35 m) and deep level (135.15 m) is determined at 650m and 1,220 m, respectively. The microthermometric data point out that the Tumpangpitu deposit formed at moderate temperature and low salinity by magmatic fluid mixing and dilution by meteoric water during the hydrothermal fluid evolution. On the basis of the fluid inclusion microthermometric data and its other key characteristics, the Tumpangpitu gold mineralization shares some similarities compared to other typical HS-epithermal gold deposits worlwide although it also shares few differences.

The Bandung bentonite deposit is located in Wonosegoro District, Boyolali Regence, Central Java. Characteristics of bentonite in this area are very important due to increase demand on bentonite in the industry. Several methods are used to characterize the bentonite in this area, such as PLM (polarizing light microscope), X-Ray Diffraction and Scanning Electron Microscope combined with EDX measurements. The montmorilonitic claystone belongs to Kerek Formation from Banyuurip Member. This deposit consists of mainly montmorilonitic claystone interbedded with tuffaceous sandstone. Petrographical analysis shows that montmorilonitic claystone consists of mostly clay minerals with small amount of calcite, volcanic glass, feldspar, quartz, and opaque minerals. The clay minerals are likely as alteration product of volcanic glass. The oriented XRD analyses show that the clay samples consist of Ca-montmorilonite, illite, and kaolinite. Physico-chemical analyses of montmorilonitic claystone display that the initial CEC (cation exchange capacity) is 20 mgrek.Na2O/200gr (54 mg.Na2O/100gr) and low swelling ability for about 2 times of its initial volume. Based on its mineralogical association, textures, and stratigraphic position, the montmorilonite is formed from devitivication of volcanic glass in a diagenetic environment with over 2 km thicks of overburden. Keywords: Bentonite, montmorillonitic claystone, devitrivication, diagenesis, montmorillonite