Gneiss is a metamorphic rock, and its density can vary depending on its mineral composition. However, the average density of gneiss is typically between 2.6 and 2.8 grams per cubic centimeter (g/cm³).

Here's why the density can vary:

* Mineral Composition: Gneiss is formed from the metamorphism of various igneous and sedimentary rocks. Different minerals have different densities, so the density of gneiss will depend on the specific minerals present.

* Texture: Gneiss has a foliated texture, meaning it has layers of different minerals. The arrangement of these layers can also affect the density.

Here's a general range for some common minerals found in gneiss:

* Quartz: 2.65 g/cm³

* Feldspar: 2.54 - 2.76 g/cm³

* Mica: 2.8 - 3.1 g/cm³

* Garnet: 3.5 - 4.3 g/cm³

* Amphibole: 2.9 - 3.3 g/cm³

Therefore, the density of a specific gneiss sample can be calculated based on its mineral composition and their proportions.