There are three kinds of rock: igneous, sedimentary, and metamorphic. Igneous rocks form when molten rock (magma or lava) cools and solidifies. Sedimentary rocks originate when particles settle out of water or air, or by precipitation of minerals from water. They accumulate in layers.

Rocks can be divided into three basic classifications: igneous, sedimentary, and metamorphic. The following tests are used by experts to classify rocks: Hardness Test – Minerals are scaled in range from 1 to 10, with 1 being softest and 10 hardest. The method of determining hardness is the scratch test.

Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth’s crust, or lava cools on the ground surface or the seabed.

Petrology is the study of rocks – igneous, metamorphic, and sedimentary – and the processes that form and transform them. Mineralogy is the study of the chemistry, crystal structure and physical properties of the mineral constituents of rocks.

pebble

nounprecious stone; treasure. bauble. glass. hardware. jewel.

flint. noun. a hard grey stone that was used in the past for making tools.

Soapstone is composed mostly of the mineral “talc”, which is the softest mineral in the world.

• Basalts. Basalts are one of the most common rock types in the world.
• Granite. Granite is an igneous rock formed from magma deep within the earth’s crust.
• Quartzite. Quartzite has similar, if not stronger, physical-mechanical features than granite.
• Limestone.
• Marble.
• Onyx.
• Semi-precious stone.
• Travertine.

The most common type of stone contains calcium. Calcium is a normal part of a healthy diet.

Navaratna is a combination of nine precious gemstones (Ruby, Diamond, Blue Sapphire, Yellow Sapphire, Emerald, Red Coral, Pearl, Cat’s eye and Hessonite) worn in a single ornament.