Solution:

Clues:

Across:

1: "Boiled stone" - ZEOLITE] (A stone that boils)
2: A type of interpolation - MIMETIC
3: A shorter word for illogicality - FALLACY
6: These often reside at the bottom - FEEDERS (Bottom of food chain)

Diagonal Up:

1: A very enthusiastic weapon modifier in Terraria - ZEALOUS (Name of a modifier)
2: An inanimate bipedal - MICYCLE (Not sure on why)
3: A rather peculiar bed that is used for transportation - FLATBED (Type of truck)
6: That which is famously not a bug - FEATURE (It's not a bug, it's a feature)

Diagonal Down:

4: One 16th in the company of four 8th ones - SULFATE (Chemical compound is S (16th element) and 4 Os (8th element)
5: A word that can describe Mrs. Incredible - ELASTIC
7: One would probably be advised to have some of it if walking down the street wearing only socks, or a hat - DECENCY
8: If you picture a pencil as a sword, these often serve as its pommel - ERASERS

Solution:

Clues:

Across:

1: "Boiled stone" - ZEOLITE (A stone that boils)
2: A type of interpolation - BICUBIC
3: A shorter word for illogicality - FALLACY
6: These often reside at the bottom - FEEDERS (Bottom of food chain)

Diagonal Up:

1: A very enthusiastic weapon modifier in Terraria - ZEALOUS (Name of a modifier)
2: An inanimate bipedal - BICYCLE
3: A rather peculiar bed that is used for transportation - FLATBED (Type of truck)
6: That which is famously not a bug - FEATURE (It's not a bug, it's a feature)

Diagonal Down:

4: One 16th in the company of four 8th ones - SULFATE (Chemical compound is S (16th element) and 4 Os (8th element)
5: A word that can describe Mrs. Incredible - ELASTIC
7: One would probably be advised to have some of it if walking down the street wearing only socks, or a hat - DECENCY
8: If you picture a pencil as a sword, these often serve as its pommel - ERASERS