Modifiers matching feldspar:

• natural,
• harder,

Simple categories matching harder:

• boot,
• fabric,
• stone,
• powder,
• material,
• music,
• metal,
• surface,
• cheese,
• genre,
• gemstone,
• aggregate,
• structure,
• drug,
• part,
• stuff,
• sport,
• alloy,
• mineral,
• stimulant,
• object,
• deposit,
• abrasive,
• substance,
• pin,
• tissue,
• ground,
• wood,
• particle,
• crystal,
• rock,
• currency,
• food,
• substrate,
• agent,
• narcotic,
• formation,
• thing,
• glass,
• polymer,
• filler,
• layer,
• sediment,
• resin,
• feldspar,
• medium,
• ingredient,
• work,
• assets,