Answer:
A
Ametrine containing amethyst and citrine, from Bolivia
Abelsonite
Abenakiite-(Ce)
Abernathyite
Abhurite
Abramovite
Althausite
Althupite
Altisite
Alum-(K)
Aluminite
Aluminium
Alunite
Alunogen
Amakinite
Amarantite
Amblygonite
Ameghinite
Amesite
Amicite
Amphibole (mineral group)
Analcime (analcite)
Anandite
Anapaite
Anatase
Ancylite (mineral group)
Andalusite
Andersonite
Andesine
Andorite (IV/VI)
Andradite
Andyrobertsite
Anglesite
Anhydrite
Ankerite
Annabergite
Annite
Anorthite
Anorthoclase
Antarcticite
Anthonyite
Anthophyllite
Antigorite
Antimony
Antitaenite
Antlerite
Apachite
Apatite (mineral group)
Aphthitalite
Apophyllite
Aragonite
Arcanite
Archerite
Arctite
Arcubisite
Ardaite
Arfvedsonite
Argentite
Argutite
Argyrodite
Armalcolite
Arsenic
Arseniosiderite
Arsenoclasite
Arsenolite
Arsenopyrite
Arthurite
Artinite
Artroeite
Ashburtonite
Ashoverite
Asisite
Astrophyllite
Atacamite
Athabascaite
Atheneite
Aubertite
Augelite
Augite
Aurichalcite
Auricupride
Aurostibite
Austinite
Autunite
Avicennite
Avogadrite
Awaruite
Axinite (mineral group)
Azurite
Varieties that are not valid species:
Adamantine spar (variety of corundum)
Agate (variety of chalcedony and quartz)
Alabaster (variety of gypsum)
Alexandrite (variety of chrysoberyl)
Allingite (synonym of amber)
Alum
Amazonite (variety of microcline)
Amethyst (purple variety of quartz)
Ametrine (variety of quartz)
Ammolite (organic; also a gemstone)
Amosite (asbestiform grunerite)
Antozonite (variety of fluorite)
Anyolite (metamorphic rock - zoisite, ruby, and hornblende)
Aquamarine (light blue variety of beryl)
Argentite (high temperature form of acanthite)
Asbestos (fibrous serpentine- or amphibole minerals)
Auerlite (variety of thorite)
Avalite (chromian variety of illite)
Aventurine (variety of quartz)
