Le grès est dur.

In French, you usually use an article with nouns, even when talking about something in general.

So:

• Le grès = sandstone as a material, in a general sense
• literally: the sandstone

French does this very often:

• Le vin est cher. = Wine is expensive.
• Le sucre est blanc. = Sugar is white.

So Le grès est dur is the normal way to say Sandstone is hard.

Grès is masculine, which is why it takes le:

• le grès

Because it is masculine singular, the adjective also stays in the masculine singular form:

• dur

If the noun were feminine, you would usually see:

• dure

French adjectives agree with the noun they describe in gender and number.

Here:

• grès = masculine singular
• so the adjective must also be masculine singular
• therefore: dur

Examples:

• Le grès est dur.
• La pierre est dure.

So the ending changes depending on the noun.

Est is the third-person singular form of the verb être, which means to be.

So:

• le grès = sandstone
• est = is
• dur = hard

That gives:

• Le grès est dur. = Sandstone is hard.

Other forms of être include:

• je suis = I am
• tu es = you are
• il est / elle est = he is / she is

Because dur is not directly placed next to the noun here. It comes after être and describes the subject through the verb.

This is a very common French pattern:

• Le ciel est bleu.
• La table est grande.
• Le grès est dur.

So the structure is:

• subject + verb + adjective

Just like in English:

• Sandstone is hard.

Grès is pronounced roughly like grey but with a French r and a shorter, more open vowel.

A simple approximation for an English speaker is:

• greh

A few useful points:

• the g is a hard g, as in go
• the r is the French r
• è gives an eh sound
• the final s is normally silent

So grès is not pronounced like English grass or grace.

The accent grave on è helps show the vowel sound.

• è usually sounds like eh
• without that accent, the pronunciation would likely be different

So in grès, the è helps signal the correct vowel sound.

It is also part of the correct spelling, so you should write:

• grès

not:

• gres

Yes. Dur can have several meanings depending on context, such as:

• hard
• tough
• harsh
• difficult

For example:

• un lit dur = a hard bed
• un travail dur = hard work
• une période dure = a hard/tough time

But in Le grès est dur, it clearly means physically hard.

Yes, you could, but it is a slightly different structure.

• Le grès est dur. = straightforward, neutral statement
• Le grès, c'est dur. = more like Sandstone, that’s hard or As for sandstone, it’s hard

The version with est is the simplest and most standard form for a basic descriptive sentence.

Usually, Le grès est dur is understood as a general statement about sandstone as a material.

That is because:

• le + noun in French can refer to a whole category or substance in a general way

So it most naturally means:

• Sandstone is hard

If you wanted to talk about one specific piece, the context would usually make that clear.