- A
-
- Abrasive
- Absolute hardness
- Absorption spectra
- Absorption spectrum
- Accessory mineral
- Acicular
- Acid
- Acid test
- Activator
- Adamantine (luster)
- Adularescence
- Adularescent
- Aggregate
- Alkaline
- Alloy
- Alloyed
- Alluvial
- Alluvial deposit
- Alluvion
- Alluvium
- Alpha rays
- Alpine cavity
- Alter
- Alteration
- Amalgam
- Amber
- Ammonia
- Ammonium hydroxide
- Amorphous
- Amphibole
- Amphibole group
- Amygdule
- Anhydrous
- Anhydrous borates
- Anion
- Anisotropic
- Anisotropism
- Anticline
- Antimonides (subgroup)
- Aqua fortis
- Aqua regia
- Aqueous
- Aragonite group
- Arborescent
- Argentiferous
- Argillacious
- Arid
- Arsenates (group)
- Arsenides (subgroup)
- Asbestos
- Asbestos amphibole
- Asterism
- Asteroid
- Asymmetrical
- Atom
- Atomic
- Atomic structure
- Atomical arrangement
- Atomically
- Auriferous
- Autochthonous
- Aventurescence
- Aventurization
- Axes
- Axis
- Axis of symmetry