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Scotlandite occurs as chisel-shaped or bladed crystals elongated along the c-axis, with a tendency to form radiating clusters. Its crystals are characterized by the {100}, {010}, {011}, {021}, {031}, and {032}. faces. Scotlandite shows perfect cleavage along the {100} plane and a less good one along the {010} plane. The measured density is 6.37 ...
Amethyst crystals – a purple quartz Apophyllite crystals sitting right beside a cluster of peachy bowtie stilbite Aquamarine variety of beryl with tourmaline on orthoclase Arsenopyrite from Hidalgo del Parral, Chihuahua, Mexico Aurichalcite needles spraying out within a protected pocket lined by bladed calcite crystals Austinite from the Ojuela Mine, Mapimí, Durango, Mexico Ametrine ...
Leightonite forms flattened to elongated bladed crystals of variously interpreted crystal structure. Its crystal system is reported as triclinic morphologically, but also as pseudo- orthorhombic due to intricate lamellar twinning that mimics orthorhombic symmetry.
It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its Mohs hardness is 5.0–6.0, and its specific gravity is 3.0–3.4. Cleavage is perfect, two directions in the shape of a diamond; fracture is uneven ...
Recognizing the habit can aid in mineral identification and description, as the crystal habit is an external representation of the internal ordered atomic arrangement. [1] Most natural crystals, however, do not display ideal habits and are commonly malformed. Hence, it is also important to describe the quality of the shape of a mineral specimen:
Graph of komatiite geochemistry MgO% vs Cr ppm, from basal flows, Wannaway, Western Australia. The pristine volcanic mineralogy of komatiites is composed of forsteritic olivine (Fo90 and upwards), calcic and often chromian pyroxene, anorthite (An85 and upwards) and chromite.
Hornblende has a hardness of 5–6, a specific gravity of 3.0 to 3.6, and is typically an opaque green, dark green, brown, or black color. It tends to form slender prismatic to bladed crystals, diamond-shaped in cross section, or is present as irregular grains or fibrous masses.
2 O, was named after John Sinkankas (1915–2002), noted author and mineral collector, Scripps Institute of Oceanography. [4] It is triclinic; as colorless, bladed to prismatic crystals up to 4 mm in length, often as divergent, radial aggregates and as pseudomorphs after triphlyte crystals; occurs in the Barker pegmatite (formerly Ferguson ...