Ramikite-(Y)

The kinds of rock environments where the mineral typically forms — igneous, metamorphic, hydrothermal, sedimentary, pegmatitic, and so on.

The place where the mineral was first found and described — by convention, the reference point for the species.

Resistance to being scratched, ranked on the Mohs scale from 1 (talc, marked by a fingernail) to 10 (diamond, scratches everything below it). The classic field test.

The hue of the mineral itself. Often unreliable for identification — many species occur in several colours depending on trace impurities or radiation damage.

The colour of a mineral's powder, drawn by scraping it across an unglazed porcelain plate. Far more consistent than surface colour.

The tendency to split along flat planes that match the crystal's atomic structure. Described by quality (perfect, good, poor) and direction.

The shape of a broken surface that doesn't follow cleavage — conchoidal (curved, like broken glass), uneven, hackly, or splintery.

Mass per unit volume, in grams per cubic centimetre. A useful sorting tool: barite is twice as dense as quartz at the same size.

How much light bends as it enters the mineral. Higher index means stronger bending — diamond's extreme index is why it sparkles.

How sharply a grain stands out against the mounting medium (Canada balsam, n ≈ 1.54) under the petrographic microscope. Low relief means the grain almost dissolves into the slide; very high relief gives crisp, almost three-dimensional outlines.

The refractive indices measured along the crystal's principal optical axes — nω and nε for uniaxial minerals, nα, nβ, and nγ for biaxial.

The difference between the highest and lowest refractive indices. Drives the interference colours seen under crossed polarisers.

The orientation, relative to crystal edges, at which a thin section goes dark between crossed polarisers. Used to separate look-alike species.

How the mineral glows under short- and long-wave ultraviolet lamps. Some species fluoresce in spectacular colours invisible to the naked eye.

One of seven geometric families that describe a mineral's atomic symmetry: isometric (cubic), tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, triclinic. Two non-crystalline classes — amorphous and icosahedral — also appear.

The full symmetry description of a crystal's repeating atomic pattern — 230 distinct groups, written in Hermann–Mauguin notation (e.g. P6₃/mmc).

The lengths of the unit-cell edges (a, b, c) in ångströms — the smallest repeating box of atoms that builds the crystal.

The angles (α, β, γ) between unit-cell edges, in degrees. Cubic crystals have 90°/90°/90°; triclinic crystals can take any combination.

Edge-length ratios of the unit cell, normalised so b = 1. Lets you compare related species without quoting absolute ångström values.

The overall shape and habit a mineral tends to grow into — cubes, prisms, plates, fibres, druses, masses.

Oriented overgrowth of one mineral on the surface of another, controlled by matching atomic spacings between the two.

The crystal habit observed at the type locality — the place where the mineral was first described.