Milky quartz (likely quartz crystal)

White to translucent, vitreous-to-waxy luster, uneven to conchoidal fracture, and no obvious cleavage. Mohs hardness 7; trigonal crystal structure; specific gravity about 2.65. The striated, blocky surfaces may reflect broken or intergrown crystal faces.

Forms when silica-rich fluids crystallize in fractures, veins, pegmatites, and hydrothermal cavities, commonly in granitic or metamorphic terrains. Exact age cannot be determined from the photograph; quartz is widespread and may range from ancient basement rocks to young veins.

Used for glass, ceramics, abrasives, engineered stone, and silicon production; attractive transparent pieces are collected or cut as cabochons. This specimen appears common and has modest gem value.

Quartz can scratch ordinary steel or glass, but it should not be confused with calcite, which is softer and commonly rhombohedral. The cloudy appearance is caused by microscopic fluid inclusions, fractures, or other mineral inclusions.

Likely identification: milky quartz, possibly with minor feldspar or clay staining. A glass-scratch test, hardness comparison, and lack of acid reaction support quartz; the Sabah location is geologically plausible for quartz-bearing veins and granitic/metamorphic rocks, though locality confirmation requires matrix and testing.