Rock Identification

Description:

Dark gray and massive quartz vein showing tightly packed interlocking crystals of variable grain size coated by pale yellow minute crystals of pyrite (FeS2) and arsenopyrite (FeAsS). Dominant vugs with or without pyrite fill. Disseminated white and fibrous (hair like) melanterite (FeSO4.7H2O) which is a product of oxidation of pyrite were present in some sections.

Alteration:

SILICIFICATION

Composition:

Quartz, Pyrite, Arsenopyrite, Melanterite

Description:

Mixture of white gray massive quartz in saccharoidal texture. Calcite crystals are observed as cavity infilling. Very fine matallic minerals, composed of pyrite and magnetite are observed in the sample. Pyrites is occasionally partly replaced by chalcopyrite. Magnetite occur as disseminations in minimal amount. Dominant minute vugs are present in the specimen.

Alteration:

SILICIFICATION

Composition:

Quartz, Calcite, Pyrite, Magnetite

Description:

Hard, brownish black rock from an original piece of wood that have completely transitioned and turned into stone by the process of petrification, wherein organic materials are replaced by silica, while ratining its original structure. Quartz (SiO2) is the main replacement mineral.

Alteration:

SILICIFICATION

Composition:

Quartz

Description:

White and massive quartz in succharoidal texture. Minimal amountys of fine-sized magnetite are observed in the sample as disseminations. Magnetitie grains are weakly magnetic due to partial alteration to hemantite.

Alteration:

SILICIFICATION

Composition:

Quartz, Calcite, Magnetitie

Description:

Gray, fine-grained and brecciated Andesite clasts. Sub-parallel fractures are nearly cemented by prismatic quartz crystals with few black hematite and rare brassy yellow chalcopyrite with greenish tinge. Cut by few quartz and calcite stringers. Abundant vugs wherein quartz crystals turns black due to iron oxide coatings. Yellowish staining was common.

Alteration:

SILICIFICATION

Composition:

Quartz, Hematite, Chalcopyrite, Calcite

Description:

Shattered, sheared, fragmented rock but cemented by rock flour and fine pieces of the same rock material. Primary texture is obliterated due to intense argillization and chloritization. Remnants of biotite characterize rock fragments. Fine pyrites are present in minimal amounts and occur as anhedral patches.

Alteration:

ARGILLIZATION, CHLORITIZATION, SILICIFICATION

Composition:

Quartz, Calcite, Pyrite, Magnetite

Description:

Greenish gray with 1-2 milimeter sized and irregular shaped lithic fragments cemented by grounded materials of the same composition as the bigger fragments. Intensely argillized and chloitized with weak calcite characterized the rock. Pale yellow pyrites are closely spread within the rock which exhibits fractured appearance and corroded surfaces. Limonite with trace of hematite was noted on fractured planes.  Sample was probably taken from a sheared zone made up of basic rock composition.

Alteration:

ARGILLIZATION AND CHLORITIZATION

Composition:

Calcite, Limonite, Hematite

Description:

Fine-grained gray matrix coated with rusty brown the exposed planes. Silicified rock having vugs with reddish brown drusy quartz (SiO2). Matrix supported composed of anhedral shape of pebble to cobble size dioritic clasts that is intensely altered to sericite. Very fine few pyrite (FeS) occurs as disseminations.\

Alteration:

SILIFICATION, ARGILIZATION

Composition:

Quartz, Pyrite

Description:

White translucent quartz (SiO2) where crystals exhibit prismatic showing elongated euhedral shapes. Cavities filled by brownish yellow sphalerite (ZnS) and black metallic galena (PbS) with few fine-grained dessiminations of cubic pyrite (FeS@) and traces of brassy yellow chalcopyrite (CuFeS2). Yellowish staining of iron oxides were noted in some sections.

Alteration:

SILICIFICATION

Composition:

Quartz, Sphalerite, Galena, Pyrite, Chalcopyrite

Description:

Fine-grained bleached Andesite porphyry coated by limonite and hematite with few manganese oxeds, silicified, surrouned by minute vugs and showing sugary crystal of quartz. Plagioclase was pseudomorphously replaced by fibrous chlorite+calcite.

Alteration:

SILICIFICATION, ARGILIZATION, OXIDATION

Composition:

Quartz, Plagioclase, Limonite, Chlorite, Calcite

Description:

Fine-grained greenish gray breccietaed rock cut by criss-crossing white quartz (SiO2) veinlets. Calcite patches are likewise noted to occur in some veinlets. Hornblendes are completely oxidized by rusty brown iron oxides and black manganese oxides. Fine pyrite (FeS2) occur as disseminations in some sections.

Alteration:

SILICIFICATION

Composition:

Quatrz, Calcite, Pyrite

Description:

Intense argillization and moderate chloritization obliterated the original texture of the rock specimen. Fragments are characterized by biotite overprinted by illite. Very fine to fine-grained pyrite (FeS) are present as disseminations with traces of magnetitie. Calcite and quartz veinlets crisscross the rock.

Alteration:

POTASSIC, ARGILLIC, PROPYLITIC

Composition:

Pyrite, Calcite, Quartz, Magnetite

Description:

Crustiform banding of microcrystalline quartz (SiO2) veins showing alternating layers of white gray parallel bands of prismatic and saccharoidal quartz. Bands thickness varies from 0.60 to 1.00 centimeter. Abundant vugs or cavities filled with limonite and hematite dust are common on the gray quartz. Staining of yellowish iron oxide was noted in some sections.

Alteration:

SILICIFICATION

Composition:

Quartz, Limonite, Hematite