Which term is defined as the ratio of the weight of a material to the weight of an equal volume of water?

Which term is defined as the ratio of the weight of a material to the weight of an equal volume of water?

• A. Growth Marks
• B. Specific Gravity
• C. Habit
• D. Point Defect

Answer: (B)

Specific gravity describes how heavy a gemstone is for its size by comparing its weight to the weight of an equal volume of water. It’s a dimensionless number, essentially a density comparison to water (water has a defined density, so SG shows how much denser the material is than water). This makes SG a useful identification tool because different gemstones have characteristic SG ranges—diamond about 3.52, quartz around 2.65, ruby and sapphire near 4.0, garnet roughly 3.5–4.3, and beryl around 2.7–2.8. SG is measured by weighing the gemstone in air and then in water (or by other density methods that apply Archimedes’ principle). The other terms are not about density. Growth marks are features from crystal growth, habit is the crystal’s external shape, and point defects are microscopic lattice imperfections. These describe structure or appearance, not how heavy the stone is relative to water.

Specific gravity describes how heavy a gemstone is for its size by comparing its weight to the weight of an equal volume of water. It’s a dimensionless number, essentially a density comparison to water (water has a defined density, so SG shows how much denser the material is than water). This makes SG a useful identification tool because different gemstones have characteristic SG ranges—diamond about 3.52, quartz around 2.65, ruby and sapphire near 4.0, garnet roughly 3.5–4.3, and beryl around 2.7–2.8. SG is measured by weighing the gemstone in air and then in water (or by other density methods that apply Archimedes’ principle).

The other terms are not about density. Growth marks are features from crystal growth, habit is the crystal’s external shape, and point defects are microscopic lattice imperfections. These describe structure or appearance, not how heavy the stone is relative to water.