The Lithic.

Your patron has stood the test of time immortalized in stone, steeped in powerful earthen magic over eons. They may be a powerful gargoyle or sphinx, a sentient gemstone, an ancient statue or even the stone itself of an entire subterranean realm. Many dwarves have sung and spoken of these patrons for millenia, often calling it the mountains will or the soul of stone. The motivations and grudges of a being such as this are patient and everlasting, for sooner or later, everything else will surely crumble to dust.

Level 1 Features:

Lithic Magic.

When you learn a spell of the appropriate level using your pact magic feature, you also learn the spells on the Lithic Spells table. The spells count warlock spells for you, and do not count against your spells known.

Major Mending.

At 1st level, you learn the Mending cantrip, which does not count against the number of warlock cantrips you know. This version of the spell allows you to mend breaks in stone up to three feet across in any dimension, instead of one.

Speak to Stone.

Also at 1st level, you can speak, read, and write Terran. In addition, you can use an action to touch a stone no larger than 30 feet in any dimension, giving it the ability to communicate with you for 10 minutes. You can question the stone about events within 30 feet of it from the past day, gaining information about creatures that have passed, the weather, local terrain, and other circumstances.
The stones maximum size, range of awareness, and time in which it can recall events increases when you gain levels in this class. The stones maximum size and range of awareness increases to 60 feet at 6th level, 90 feet at 10th level, and 120 feet at 14th level. Similarly, the time in which the stone can recall information increases to 7 days at 6th level, 30 days at 10th level, and 90 days at 14th level.
You can use this feature a number of times equal to your Intelligence or Charisma modifier (a minimum of once). You regain all expended uses when you finish a long rest.

Level 6 Feature:

Heart of Stone.

At 6th level, you understand the very nature of stone itself. You can not be petrified against your will, and moving through difficult terrain created by stone costs you no extra movement. If you are petrified, you can use a bonus action to end the effect on yourself, even if you are incapacitated. You can also cast the Illusory Script and Magic Mouth spells, but only as a ritual. These versions of the spells don not require any material components, but must target an object that's made of stone. A spells effect ends early if you use this feature to cast it again.
In addition, you can use a bonus action to become petrified, becoming indistinguishable from an ordinary statue. You remain petrified for up to 1 hour or until you use a bonus action to end the effect. While petrified, you have blindsight and tremorsense out to a range of 10 feet and can hear. Further, you do not need to breathe for the duration, and you and are not considered to be incapacitated, although you still can not take any actions or reactions (except for the bonus action to end the effect). You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Level 10 Feature:

Invoke Earth.

At 10th level, you can use an action to expend a use of your Heart of Stone feature to transform into an earth elemental, as if by the polymorph spell, without requiring concentration. You remain transformed for 1 hour or until you end the effect as a bonus action or are reduced to 0 hit points.
You retain your alignment, personality, and Intelligence, Wisdom, and Charisma scores. You also retain all of your skill and saving throw proficiencies. Once you use this feature, you can not do so again until you finish a long rest.
Once you reach 14th level in this class, you can make a third Slam attack as an earth elemental whenever you take the Multiattack action.

Level 14 Feature:

Living Statue.

By 14th level, you suffer none of the frailty of old age, and you can not be aged magically. You can still die of old age, however. You always have blindsight and tremorsense out to a range of 10 feet, even if you are not petrified. If you are petrified, the range of these senses is increased to 30 feet for the duration, and you can still speak.
Finally, you can use an action to cast the Flesh to Stone spell. You can not do so again until after you finish a long rest. If you target yourself with the spell, you can choose to fail the saving throws against it.