5 words for FOSTU 1-letter words

Filter answers for the "fostu" by length:
Sort
Alphabet (A–Z)
Alphabet (Z–A)
Scrabble score

1 letter (5)

f o s t u
Form of quartz with coloured bands
?
A
?
G
?
A
?
T
?
E
Hint 1 meaning
A semipellucid, uncrystallized variety of quartz, presenting various tints in the same specimen. Its colors are delicately arranged in stripes or bands, or blended in clouds.
Hint 2 anagram
EAAGT
Hint 3 another clue
CERTAIN BRAIN SIZE
5 +1