Other

Ramsdellite Group

Red Coral

Hardness: 3 - 4

Retzian Group

Reyerite Group

Rhabdophane Group

Rhodesite Group

Gem

Rhodolite

Hardness: 7 - 7.5

Rhodonite Group

Rinneite Group

Rockbridgeite Group

Roméite Group

Rosasite Group

Roscherite Group

Rose Quartz

Hardness: 7

Roselite Group

Routhierite Group

Rozenite Group

Ruby in Kyanite

Rudraksha

Ruizite Group

Rutile Group

Samarskite Group

Sand

Hardness: 7

Sanjuanite-destinezite Group

Sapphirine Supergroup

Sarcopside Group

Sardonyx

Hardness: 6.5 - 7

Sartorite Group

Sborgite Group

Scapolite Group

Schalenblende

Hardness: 3.5 - 4

Scheelite Group

Schoepite Group

Schoonerite Group

Sea Glass

Hardness: 5.5-7

Sedimentary

Seidozerite Supergroup

Selenite

Hardness: 1.5-2

Selenium Group

Sepiolite Group

Septarian

Hardness: 3-4

Shell

Hardness: 2.5-3.5

Shiva Shell

Hardness: 3 - 4

Shungite

Hardness: 3.5 - 4

Silver Amalgam Group

Sklodowskite Group

Slag

Hardness: 5.5 - 7

Smectite Group

Smoky Quartz

Hardness: 7

Smolyaninovite Group

Snowflake Obsidian

Hardness: 5-5.5

Sodalite

Hardness: 5.5 to 6

Sodium Amphibole Subgroup

Sodium-calcium Amphibole Subgroup

Gem

Spessartine

Hardness: 7 - 7.5

Sphalerite Group

Sphene

Hardness: 5 - 5.5

Spinel Supergroup

Spiny Oyster Shell

Hardness: 3.5

Spiroffite Group