Question

Which one of the following textures shows cuneiform-shape intergrowth between alkali feldspar and quartz?

• A. Spherulite texture
• B. Graphic texture
• C. Porphyritic texture
• D. Spinifex texture

Answer 1

The Correct Option is B

The question asks for the texture that shows cuneiform-shape intergrowth between alkali feldspar and quartz. Let's look at the options individually:

1. Spherulite texture: This texture is characterized by radiating needle-like crystals generally made of quartz and feldspar. It does not feature the cuneiform intergrowth typical of alkali feldspar and quartz.
2. Graphic texture: This texture is well-known for its cuneiform or wedge-shaped intergrowths. In this type of texture, the quartz and alkali feldspar are intergrown in such a manner that they resemble cuneiform writing or hieroglyphs. This makes it the correct answer.
3. Porphyritic texture: This texture involves large crystals, known as phenocrysts, embedded in a fine-grained groundmass. It does not have the specific intergrowth pattern of cuneiform shapes made by quartz and feldspar.
4. Spinifex texture: Found commonly in ultramafic rocks, it features needle-like olivine crystals and is unrelated to the cuneiform texture seen in graphic textures.

The correct answer is Graphic texture due to its distinctive appearance resembling ancient writing, which results from the intergrowth of alkali feldspar and quartz.