Question

During a hike in Utah's Zion National Park, you pick up a sedimentary rock sample. When you examine the sample with your hand lens, you see that the rock consists mainly of rounded glassy particles that appear to be quartz. To be sure, you conduct two basic tests. When you check for hardness, the rock easily scratches glass, which is what quartz would do. However, when you place a drop of acid on the sample, it fizzes. Explain how a rock that appears to be rich in quartz could effervesce with acid.

Answer 1

Quartz is not pure in this rock.

Step-by-step explanation:

When quartz shows effervescence in contact with an acid, it means that it is not in its pure state, but rather related to other substances that may be cementing the quartz. This effectiveness is caused by substances that do not react like quartz, such as calcite.

In this case, we can conclude that in relation to the calcium-rich rock shown in the question above, the calcium is not pure, but it is likely to be related to calcite, or other material that does not react to acid.