Ice block
Lime stone varies from crumbly to almost as hard as flint, depending mostly on how much weight was above it when it was being formed.
Plaster of Paris is a substance that becomes hard when mixed with water. It is commonly used in construction and arts and crafts for making molds and sculptures.
The water was evaporated.
When water is added to a metallic oxide, it forms a metal hydroxide (also known as basic oxide) and releases heat in an exothermic reaction. For example, when water is added to calcium oxide, it forms calcium hydroxide.
salt
Hardness is the question of how difficult it is to make an impression on a substance. Brittleness is the question of how easy it is to break. Granite is a stone which is very hard but not brittle--it is hard to carve and also hard to break. A plank of wood is not as hard as stone but is not very brittle. You can carve on it with a knife but it won't shatter if you drop it. Glass is hard and brittle. Chalk is not hard but it is brittle.
No, an aquamarine stone will not disappear if placed in water. Aquamarine is a type of beryl mineral, which is a hard and durable gemstone. It will not dissolve in water or disappear.
A kidney stone is a hard deposit of minerals and salts that forms in the kidneys. It can be very painful as it passes through the urinary tract. Drinking plenty of water and making dietary changes can help prevent their formation.
Diluted bleach can clean stone brick stucco. Often gentle water pressure can remove hard water stains on stucco as well.
Clay soil can become hard as stone when it dries out due to its fine particles that compact tightly together when water evaporates. This compaction can make it difficult for roots to penetrate and hinder water drainage.
Mineral deposits from use of hard water.
No Pokemon evolves by hard stone. Hard stone just increases the power of rock type moves.