Red Quartz 
(see also Harlequin Quartz)
Location: Spain 
This is quartz with hematite.
Variety of Quartz
Chemical Composition: SiO2 and Fe2O3
Hardness: 7

Rhodochrosite
(also called raspberry spar or manganese spar)
Location: Colorado
Chemical Composition: MnCO3, Manganese Carbonate
Hardness: 3.5 - 4
 

Rhodonite
Location: Madagascar
Chemical Composition: (Mn, Fe, Mg, Ca)SiO3 manganese silicate
Hardness: 5.5 - 6.5

Rose Quartz Crystals
Location: Brazil
Light rose to a deep rose color
RARE Variety of: Quartz
Chemical Composition: SiO2 
Hardness: 7 
 

Ruby crystals in matrix
Location: Jagdalak Afghanistan
Variety of: Corundum
Chemical Composition: Al2O3
Hardness: 9

Ruby-in-Zoisite 
Location: Madagascar
Chemical Composition of Zoisite: Ca2Al3(SiO4)3(OH), Calcium Aluminum Silicate Hydroxide
Hardness: 6 - 7

Rutilated Quartz
Location: Brazil
Variety of: Quartz
Quartz chemical composition: SiO2 
Rutile chemical composition: TiO2 
Hardness: quartz 7, rutile 6 to 6.5

Selenite 
Location:  Fuentes de Ebro, Zaragoza Spain
"Selenite" is the colorless and transparent variety of gypsum that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the Greek word for Moon and means moon rock.
Chemical Composition: CaSO4-2(H2O), Hydrated Calcium Sulfate
Hardness: 2 and can be scratched by a fingernail

Septarian 
Location: Henry Mountains of Utah. 
Chemical Composition: CaCO3
The inside gold colored crystals are calcite and the brown banding is iron calcite. The outer surface was originally mud which, over millions of years, hardened into rock.

Smoky Quartz Elestial
Location: Brazil
Variety of: Quartz 
Chemical Compisition: SiO2
Hardness: 7

Stibnite 
Location: Romania
Chemical Composition: Sb2S3, Antimony Sulfide
Hardness: 2

Sugilite with bustamite

Location: Africa
Chemical Composition: KNa2Li3(Fe, Mn, Al)2Si12O30, Potassium Sodium Lithium Iron Manganese Aluminum Silicate
Hardness: 6 - 6.5

Sulfur
Location: Baja Mexico
Translucent resinous yellow
Chemical Composition: S , Elemental Sulfur
Hardness: 2