Some mountains generate with very little stone, as shown in the photo. This is on a default world type.

Example 1: (Jagged peaks)

Seed: 34752912104976

Coordinates: 43, 192, -20

Example 2: (Stony peaks)

Seed: 868565863016403259

Coordinates: -89, 117, 181

Steps to Reproduce:
1. Load up a new world
2. Find a mountain biome (Preferably jagged or stony peaks)                    

Observed Results:

After a few tries a mountain generating incorrectly (Like in the pictures provided) may be seen. The mountain has almost all of its blocks missing. I've tried it with many mountains and this bug seems to affect 1 in 5 mountains. 

Expected Results:

The mountain should generate like normal.