Mineral Identification and Properties

The video tutorial examines a thin section of a rock, likely an igneous type, under plain and cross-polarized light. It describes the grain boundaries, relief, and color of minerals such as olivine, feldspar, and pyroxene. The rock is identified as olivine gabbro, characterized by coarse-grained, interlocking crystals of similar size, with anhedral to subhedral shapes and random orientation. Key features include high relief, interference colors, and lack of pleochroism in olivine, as well as the presence of plagioclase feldspar and pyroxene.

What type of rock is suggested by the absence of sub-angular grains and banded appearance?

• Sedimentary

• Metamorphic

• Igneous

• Limestone

Which mineral is described as anhedral to subhedral and does not show pleochroism?

• Calcite

• Mica

• Olivine

• Quartz

What is the appearance of feldspar crystals under plain polarized light?

• Opaque with no twinning

• Pale yellow and pleochroic

• Low relief and slightly cloudy

• High relief and bright colors

Which mineral shows weak pleochroism and a pale brown to green color?

• Pyroxene

• Quartz

• Feldspar

• Olivine

What characteristic helps identify olivine under cross polars?

• 87-degree cleavage

• Low relief

• Multiple twinning

• Bright second order interference colors

Which mineral is identified by low first order gray to white interference colors and twinning?

• Olivine

• Quartz

• Pyroxene

• Plagioclase Feldspar

What is the characteristic cleavage angle of pyroxene that is not visible in the section?

• 60 degrees

• 90 degrees

• 87 degrees

• 45 degrees

What is the size of the crystals in the rock described in the summary?

• 1 to 2 millimeters

• Less than 1 millimeter

• Exactly 2 millimeters

• Greater than 2 millimeters

What is the name of the rock identified in the summary?

• Diorite

• Olivine Gabbro

• Basalt

• Granite

What is the orientation of the crystals in the rock?

• Layered

• Aligned

• Parallel

• Random